Conversion Of Methionine Research Articles

The role of the mitochondrial trans-sulfuration in cerebro-cardio renal dysfunction during trisomy down syndrome.

One in 700 children is born with the down syndrome (DS). In DS, there is an extra copy of X chromosome 21 (trisomy). Interestingly, the chromosome 21 also contains an extra copy of the cystathionine beta synthase (CBS) gene. The CBS activity is known to contribute in mitochondrial sulfur metabolism via trans-sulfuration pathway. We hypothesize that due to an extra copy of the CBS gene there is hyper trans-sulfuration in DS. We believe that understanding the mechanism of hyper trans-sulfuration during DS will be important in improving the quality of DS patients and towards developing new treatment strategies. We know that folic acid "1-carbon" metabolism (FOCM) cycle transfers the "1-carbon" methyl group to DNA (H3K4) via conversion of s-adenosyl methionine (SAM) to s-adenosyl homocysteine (SAH) by DNMTs (the gene writers). The demethylation reaction is carried out by ten-eleven translocation methylcytosine dioxygenases (TETs; the gene erasers) through epigenetics thus turning the genes off/on and opening the chromatin by altering the acetylation/HDAC ratio. The S-adenosyl homocysteine hydrolase (SAHH) hydrolyzes SAH to homocysteine (Hcy) and adenosine. The Hcy is converted to cystathionine, cysteine and hydrogen sulfide (H2S) via CBS/cystathioneγ lyase (CSE)/3-mercaptopyruvate sulfurtransferase (3MST) pathways. Adenosine by deaminase is converted to inosine and then to uric acid. All these molecules remain high in DS patients. H2S is a potent inhibitor of mitochondrial complexes I-IV, and regulated by UCP1. Therefore, decreased UCP1 levels and ATP production can ensue in DS subjects. Interestingly, children born with DS show elevated levels of CBS/CSE/3MST/Superoxide dismutase (SOD)/cystathionine/cysteine/H2S. We opine that increased levels of epigenetic gene writers (DNMTs) and decreased in gene erasers (TETs) activity cause folic acid exhaustion, leading to an increase in trans-sulphuration by CBS/CSE/3MST/SOD pathways. Thus, it is important to determine whether SIRT3 (inhibitor of HDAC3) can decrease the trans-sulfuration activity in DS patients. Since there is an increase in H3K4 and HDAC3 via epigenetics in DS, we propose that sirtuin-3 (Sirt3) may decrease H3K4 and HDAC3 and hence may be able to decrease the trans-sulfuration in DS. It would be worth to determine whether the lactobacillus, a folic acid producing probiotic, mitigates hyper-trans-sulphuration pathway in DS subjects. Further, as we know that in DS patients the folic acid is exhausted due to increase in CBS, Hcy and re-methylation. In this context, we suggest that folic acid producing probiotics such as lactobacillus might be able to improve re-methylation process and hence may help decrease the trans-sulfuration pathway in the DS patients.

Integrated molecular and quantum mechanical approach to identify novel potent natural bioactive compound against 2′-O-methyltransferase (nsp16) of SARS-CoV-2

With the advent of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) outbreak, efforts are still in progress to find out a functional cure for the infection. Among the various protein targets, nsp16 capping protein is one of the vital targets for drug development as it protects the virus against the host cell nucleases and evading innate immunity. The nsp16 protein forms a heterodimer with a co-factor nsp10 and triggers 2′-O-methyltransferase activity which catalyzes the conversion of S-adenosyl methionine into S-adenosyl homocysteine. The free methyl group is transferred to the 2′-O position on ribose sugar at the 5′ end of mRNA to form the cap-1 structure which is essential for replication of the virus and evading the innate immunity of the host. In this study, we identify a potential lead natural bioactive compound against nsp16 protein by systematic cheminformatic analysis of more than 144k natural compounds. Virtual screening, molecular docking interactions, ADMET profiling, molecular dynamics (MD) simulations, molecular mechanics-generalized born surface area (MM-GBSA), free energy analysis and density functional theory analysis were used to discover the potential lead compound. Our investigation revealed that ZINC8952607 (methyl-[(6-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-yl)aminomethyl]BLAHone) has the greatest binding affinity and best pharmacokinetic parameters due to presence of carbazol and BLAHone (biaryl moiety). Further, time-dependent MD simulation analysis substantiates the stability and rigidness of nsp16 protein even after interaction with the lead compound. We believe that the compound ZINC8952607 might establish as a novel natural drug candidate against CoVID-19 infection. Communicated by Ramaswamy H. Sarma

Abstract 1095: Exploiting altered methionine metabolism to overcome treatment resistance in glioblastoma

Abstract Glioblastoma (GBM) is the most aggressive adult brain tumor and is uniformly fatal due to resistance to standard therapies such as radiation (RT) and chemotherapy. Our group and others have identified altered metabolism as a key mediator of GBM RT resistance. Methionine is an essential sulfur-containing amino acid that cells use to synthesize antioxidants, polyamines and S-adenosyl methionine (SAM), which drives intracellular methylation reactions. Methionine uptake is dramatically elevated in GBM compared to normal brain, but what GBMs use this methionine for, and whether it governs GBM treatment resistance, is unknown. Here, we find that RT acutely increases the levels of numerous methionine-related metabolites in multiple RT-resistant GBM models. To interrogate metabolic pathway activity, we used 13C5 methionine stable isotope tracing to show that GBMs respond to RT by activating the conversion of methionine to SAM, which is dependent on signaling through the DNA damage response. We developed in vivo methionine stable isotope tracing techniques to confirm these findings in orthotopic PDX models of GBM. Blocking the conversion of methionine to SAM, through pharmacologic inhibition of methionine adenosyltransferase 2A (MAT2A), slowed the repair of RT-induced DNA damage and increased cell death in GBM models following RT. These effects were especially pronounced in GBM models lacking the methionine salvage enzyme methylthioadenosine phosphorylase (MTAP). Pharmacologic inhibition of MAT2A in flank and orthotopic in vivo GBM models depleted SAM levels and slowed tumor growth when combined with RT. Combining MAT2A inhibition with dietary methionine restriction and RT slowed GBM tumor growth even further. Together, our work demonstrates a new signaling link between DNA damage and methionine-driven SAM synthesis in GBM. Inhibiting SAM synthesis slows the repair of RT-induced DNA damage and augments RT efficacy. This therapeutic strategy may be especially effective in GBMs defective in methionine salvage and spare normal cortex in which methionine salvage is active. Citation Format: Navyateja Korimerla, Kari-Wilder Romans, Peter Kalev, Ayesha Kothari, Nathan Qi, Charles Evans, Maureen Kachman, Marc L Hyer, Katya Marjon, Taryn Sleger, Daniel R Wahl. Exploiting altered methionine metabolism to overcome treatment resistance in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1095.

Tryptophan Metabolism Acts as a New Anti-Ferroptotic Pathway to Mediate Tumor Growth.

Emerging evidence reveals that amino acid metabolism plays an important role in ferroptotic cell death. The conversion of methionine to cysteine is well known to protect tumour cells from ferroptosis upon cysteine starvation through transamination. However, whether amino acids-produced metabolites participate in ferroptosis independent of the cysteine pathway is largely unknown. Here, the authors show that the tryptophan metabolites serotonin (5-HT) and 3-hydroxyanthranilic acid (3-HA) remarkably facilitate tumour cells to escape from ferroptosis distinct from cysteine-mediated ferroptosis inhibition. Mechanistically, both 5-HT and 3-HA act as potent radical trapping antioxidants (RTA) to eliminate lipid peroxidation, thereby inhibiting ferroptotic cell death. Monoamine oxidase A (MAOA) markedly abrogates the protective effect of 5-HT via degrading 5-HT. Deficiency of MAOA renders cancer cells resistant to ferroptosis upon 5-HT treatment. Kynureninase (KYNU), which is essential for 3-HA production, confers cells resistant to ferroptotic cell death, whereas 3-hydroxyanthranilate 3,4-dioxygenase (HAAO) significantly blocks 3-HA mediated ferroptosis inhibition by consuming 3-HA. In addition, the expression level of HAAO is positively correlated with lipid peroxidation and clinical outcome. Together, the findings demonstrate that tryptophan metabolism works as a new anti-ferroptotic pathway to promote tumour growth, and targeting this pathway will be a promising therapeutic approach for cancer treatment.

In silico characterization of fructosyl peptide oxidase properties from Eupenicillium terrenum.

Fructosyl peptide oxidase (FPOX) enzyme from Eupenicillium terrenum has a high potential to be applied as a diagnostic enzyme. The aim of the present study is the characterization of FPOX from E. terrenum using different bioinformatics tools. The computational prediction of the RNA and protein secondary structures of FPOX, solubility profile in Escherichia coli, stability, domains, and functional properties were performed. In the FPOX protein, six motifs were detected. The d-amino acid oxidase motif was found as the most important motif that is a FAD-dependent oxidoreductase. The cysteines including 97, 154, 234, 280, and 360 showed a lower score than -10 that have a low possibility for participitation in the formation of the SS bond. The 56.52% of FPOX amino acids are nonpolar. Random coils are dominant in the FPOX sequence, followed by alpha-helix and extended strand. The fpox gene is capable of generating a stable RNA secondary structure (-423.90 kcal/mol) in E. coli. FPOX has a large number of hydrophobic amino acids. FPOX showed a low solubility in E. coli which has several aggregation-prone sites in its 3-D structure. According to the scores, the best mutation candidate for increasing solubility was the conversion of methionine 302 to arginine. The melting temperature of FPOX based on its amino acid sequence was 55°C to 65°C. The amounts of thermodynamic parameters for the FPOX enzyme were -137.4 kcal/mol, -3.59 kcal/(mol K), and -6.8 kcal/mol for standard folding enthalpy, heat capacity, and folding free energy, respectively. In conclusion, the in silico study of proteins can provide a valuable method for better understanding the protein properties and functions for use in our purposes.

A novel ratiometric fluorescent probe for the detection and imaging of cysteine in living cells

Cysteine is an essential amino acid for humans and can be generated from the conversion of methionine or the interconversions with cystine. The detection of cysteine in the living system is of great importance for the diagnosis of related diseases. Based on the classical cysteine response mechanism, the sulfhydryl group of cysteine undergoes Michael addition with the acrylate to rapidly respond to form a seven-membered ring that specifically recognizes cysteine. In the present work, we designed a novel ratiometric fluorescent probe N-1, which contained the benzo[cd]indol fluorophore and the response group acrylate. As the concentration of cysteine increased, the fluorescence of I485 was significantly enhanced while the fluorescence intensity at 635 nm was weakened. Moreover, probe N-1 showed excellent sensitivity and selectivity to Cys with the calculated LOD of 4.0 × 10-9 M. Probe N-1 was successfully used for imaging cysteine in the living Hela cells with low cytotoxicity, indicating that this ratiometric fluorescent probe would be a novel and useful tool to monitor cysteine in the physiological or pathological processes.

Study Significance of Low Plasma Homocysteine or Hypohomocysteinemia and Some Parameter to Syndrome Associated with COVID-19 in Basrah City, Iraq

The increasing interdependence between the countries of the world has led to an increase in the risks faced by societies in general. The COVID-19 pandemic, for example, has transcended national borders, affecting people regardless of nationality, level of education, income or gender. As for its consequences, it has affected the most vulnerable groups. In this study, we have considered the significance of low plasma homocysteine or hypohomocysteinemia and some parameters of the syndrome associated with COVID-19. Just as an increase in the level of homocysteine in plasma has a negative effect on the heart and blood vessels, its decrease may put the health of those who suffer from it at risk. Homocysteine is known to be the natural mediator of the conversion of methionine to cysteine; hence, the danger, as the latter is necessary for the production of glutathione, taurine and sulphate. In this study, homocysteine and some indicators of COVID-19 syndrome were examined using ELISA kit and other methods. The homocysteine level in the serum of people who recovered from COVID-19 was found to be lower than in normal and healthy people. Thus, it indicates that people who have been cured may suffer from hypohomocystinemia. We also study some parameters, such as ALP, GOT, GPT, Glucose level and HDL, cholesterol. The results showed a significant decrease in the level of GOT enzyme and HDL level.

DNA Methylation Underlies the Long‐Term Association Between Periodontitis and Atherosclerotic Cardiovascular Disease

Periodontitis, one of the most common inflammatory conditions, and the leading cause of adult tooth loss, has been identified as an independent risk factor for cardiovascular disease (CVD). Long‐term studies in edentulous patients with a history of periodontitis showed persistence of increased CVD risk for years after edentulism, suggesting that clinical elimination of disease is not sufficient in decreasing periodontitis‐induced CVD risk. This is similar to other CVD risk factors, such as smoking and diabetes. We hypothesized that periodontitis induces epigenetic changes in hematopoietic stem cells in the bone marrow (BM), and such changes persist after clinical elimination of the disease and underlie the induced‐CVD risk.To simulate clinical elimination of periodontitis and persistence of the hypothesized epigenetic reprogramming, we used a BM transplant approach. Using the low density lipoprotein receptor (LDLR) KO atherosclerosis mouse model, BM donor mice were fed a high fat diet (HFD) to induce atherosclerosis, and orally inoculated with Porphyromonas gingivalis(Pg), a keystone periodontal pathogen, to induce periodontitis; a second group was sham inoculated. (We previously showed that HFD‐fed, Pginoculated mice developed more atherosclerosis than sham‐inoculated). Naïve LDLR KO mice were irradiated and transplanted with BM from one of the 2 donor groups.Recipients of BM from Pg‐inoculated donors developed significantly more atherosclerosis, accompanied by more pro‐inflammatory plasma and macrophage cytokine profiles. Using whole genome bisulfite sequencing, 375 differentially methylated regions (DMR), and a global hypomethylation in recipients of BM from Pg‐inoculated donors, were identified. Some DMRs pointed to involvement of enzymes with major roles in methylation and demethylation. In recipients of BM from Pg‐inoculated donors, methionine adenosyl transferase (MAT), which catalyzes the conversion of methionine to S‐denosylmethionine (SAM), the universal methyl‐donor, was hypermethylated. The gene for S‐adenosylhomocysteine hydrolase, which catalyzes the reversible conversion of the potent methylation inhibitor, S‐adenosylhomocysteine (SAH), to homocysteine and adenosine, was also hypermethylated. In contrast, the de‐methylation enzyme, Ten‐Eleven Translocase (TET) 2, was hypomethylated. In validation assays, we found a significant increase in activity of TET2 and a decrease in activity of DNA methyltransferases. Plasma SAH levels were significantly higher and the SAM to SAH ratio was decreased, both of which have been associated with CVD. Homocysteine, is at the intersection of the methionine cycle and the transsulphuration pathway, where it can either be re‐methylated to methionine and go through the methionine cycle, or it can synthesize cysteine through the transsulphuration pathway. Glutathione, a critical antioxidant, is the end‐product of the transsulphuration pathway. In conditions of oxidative stress, the transsulphuration pathway is favored over the methionine cycle. Periodontitis is associated with oxidative stress. These data suggest a paradigm shifting mechanism linking epigenetic changes in gene methylation with the long term association between periodontitis and atherosclerotic CVD.

Molecular Insight into the Effect of a Single-Nucleotide Polymorphic Variation on the Structure and Dynamics of Methionine Synthase Reductase and Its Association with Neural Tube Defects.

Neural tube defects (NTDs) are among the common and severe congenital malformations in neonates. According to a WHO report, nearly three lakh babies are affected per year worldwide by NTDs. Most studies revealed that folate deficiency is the key element to promote NTD with other oligogenic and multifactorial elements. This folate is metabolized by the FOCM (folate one-carbon metabolism) pathway. The most important step in the FOCM pathway is the conversion of methionine to homocysteine, which is guided by the enzyme MTRR. Several single-nucleotide polymorphisms (SNPs) in the MTRR gene are strongly associated with the progression of NTD. A nonsynonymous allelic variant (rs1532268) of the protein leads to a missense mutation at the 202nd position from serine to leucine (S202L) and is associated with a higher disease prevalence in different populations. In our study, this SNP indicates a 2-fold increase in the risk of disease progression (p-value of 0.03; OR 2.76; 95% CI 1.08–7.11). Here, extensive molecular dynamics simulations and interaction network analysis reveal that the change of 202nd serine to leucine alters the structures of the FAD and NAD binding domains, which restricts the ligand binding. The S202L variation alters the functional dynamics that might impede the electron transport chain along the NADP(H)→ FAD→ FMN pathway and hamper phosphorylation by kinases like GSK-3 and CaM-II during the posttranscriptional modification of the protein. The present study provides functional insights into the effect of the genetic variations of the MTRR gene on the NTD disease pathogenesis.

Association between serum homocysteine levels and methylene-tetrahydrofolate-reductase gene polymorphism in patients with stroke: A study from a tertiary care teaching hospital from Central India

Background: Hyperhomocysteinemia (HHcy) is a well-established risk factor for vascular thrombosis leading to stroke. Homocysteine (Hcy) is mainly synthesized in the methionine cycle, and it is an intermediate during the conversion of methionine to cysteine. HHcy can develop by polymorphism of several enzymes like methylene-tetrahydrofolate-reductase (MTHFR) mutation and due to deficiency of co-factor Vitamins such as B12, B6, and folic acid. This study was planned to see the association between HHcy and MTHFR gene polymorphism in patients with stroke in populations from central India. Methods: Seventy-two patients diagnosed with stroke aged 18 years and above who met the inclusion criteria were selected. Hcy level and MTHFR mutation were identified among patients of stroke. Results: Forty-two patients (58.33%) were diagnosed with acute ischemic stroke as compared to cerebral venous thrombosis (30, 41.66%) from a total of 72 patients. The statistical analysis projected that the HHcy diagnosed among more (45, 62.5.0%) cases with stroke who had aged ≤45 years as compared to cases who had aged >45 years (17, 23.6%). None of our patients tested positive for either CT (Heterozygous) or TT(Homozygous) genotypes. Conclusions: HHcy is not associated with MTHFR gene mutation in our study group, and this possibly is related to the deficiency of co-factors in Hcy metabolism. Young age group stroke patients have higher Hcy levels.

Volatiles from the fungal phytopathogen Penicillium aurantiogriseum modulate root metabolism and architecture through proteome resetting.

Volatile compounds (VCs) emitted by the fungal phytopathogen Penicillium aurantiogriseum promote root growth and developmental changes in Arabidopsis. Here we characterised the metabolic and molecular responses of roots to fungal volatiles. Proteomic analyses revealed that these compounds reduce the levels of aquaporins, the iron carrier IRT1 and apoplastic peroxidases. Fungal VCs also increased the levels of enzymes involved in the production of mevalonate (MVA)-derived isoprenoids, nitrogen assimilation and conversion of methionine to ethylene and cyanide. Consistently, fungal VC-treated roots accumulated high levels of hydrogen peroxide (H2 O2 ), MVA-derived cytokinins, ethylene, cyanide and long-distance nitrogen transport amino acids. qRT-PCR analyses showed that many proteins differentially expressed by fungal VCs are encoded by VC non-responsive genes. Expression patterns of hormone reporters and developmental characterisation of mutants provided evidence for the involvement of cyanide scavenging and enhanced auxin, ethylene, cytokinin and H2 O2 signalling in the root architecture changes promoted by fungal VCs. Our findings show that VCs from P. aurantiogriseum modify root metabolism and architecture, and improve nutrient and water use efficiencies through transcriptionally and non-transcriptionally regulated proteome resetting mechanisms. Some of these mechanisms are subject to long-distance regulation by photosynthesis and differ from those triggered by VCs emitted by beneficial microorganisms.

Energy Dispersive Spectroscopy (EDS) Measurements of Sulfur Uptake in Pigeon Bone Associated with the Intake of Slag, and the Induction of Homocystinuria

Slag from nickel smelting operations over the last 150 years has been deposited over vast areas of soil around the Sudbury basin in Ontario, Canada. This metal-rich material containing a 2.50 ± 0.50% sulfur concentration by mass, when ingested, has the potential to effect important physiological changes in biological systems. In this work, we measure the uptake of sulfur in the tibio-tarsal bones of pigeons (Columbia Livia Domestica) subjected to a slag-based diet, using energy dispersive spectroscopy (EDS). A sulfur-rich diet is associated with homocystinuria, a condition which impairs the conversion of methionine to cysteine. Among the bony changes associated with the condition are osteopenia, loss of calcium, compromised mechanical integrity, and increased resorption. In previous work, we have detected and quantified all of these changes, and thus propose that the results of the present work support the conclusion that a sulfur-rich, slag-based diet, can induce homocystinuric condition in this avian species.<div><br></div>

Methionine Availability in the Arthropod Intestine Is Elucidated through Identification of Vibrio cholerae Methionine Acquisition Systems.

While only a subset of Vibrio cholerae strains are human diarrheal pathogens, all are aquatic organisms. In this environment, they often persist in close association with arthropods. In the intestinal lumen of the model arthropod Drosophila melanogaster, methionine and methionine sulfoxide decrease susceptibility to V. cholerae infection. In addition to its structural role in proteins, methionine participates in the methionine cycle, which carries out synthetic and regulatory methylation reactions. It is, therefore, essential for the growth of both animals and bacteria. Methionine is scarce in some environments, and the facile conversion of free methionine to methionine sulfoxide in oxidizing environments interferes with its utilization. To ensure an adequate supply of methionine, the genomes of most organisms encode multiple high-affinity uptake pathways for methionine as well as multiple methionine sulfoxide reductases, which reduce free and protein-associated methionine sulfoxide to methionine. To explore the role of methionine uptake and reduction in V. cholerae colonization of the arthropod intestine, we mutagenized the two high-affinity methionine transporters and five methionine sulfoxide reductases encoded in the V. cholerae genome. We show that MsrC is the sole methionine sulfoxide reductase active on free methionine sulfoxide. Furthermore, in the absence of methionine synthesis, high-affinity methionine uptake but not reduction is essential for V. cholerae colonization of the Drosophila intestine. These findings allow us to place a lower limit of 0.05 mM and an upper limit of 0.5 mM on the methionine concentration in the Drosophila intestine.IMPORTANCE Methionine is an essential amino acid involved in both biosynthetic and regulatory processes in the bacterial cell. To ensure an adequate supply of methionine, bacteria have evolved multiple systems to synthesize, import, and recover this amino acid. To explore the importance of methionine synthesis, transport, and recovery in any environment, all of these systems must be identified and mutagenized. Here, we have mutagenized every high-affinity methionine uptake system and methionine sulfoxide reductase encoded in the genome of the diarrheal pathogen V. cholerae We use this information to determine that high-affinity methionine uptake systems are sufficient to acquire methionine in the intestine of the model arthropod Drosophila melanogaster but are not involved in virulence and that the intestinal concentration of methionine must be between 0.05 mM and 0.5 mM.

Homocysteine Levels in Patients with Human Immunodeficiency Virus and Acquired Immunodeficiency Syndrome in Ibadan

Introduction: Homocysteine is produced from the conversion of methionine to cysteine. Conditions resulting in hyper homocysteinemia leads to an increased risk of both arterial and venous thromboembolisms by about 2 fold. 20% of HIV infected patients with objective evidence of venous thromboembolism are found to be thrombophilic with higher homocysteine levels. We enquired into homocysteine levels prior to the development of a clinical evidence of a venous thrombus in both HAART naïve and those on HAART of HIV /AIDS population. We evaluated the association between homocysteine, CD4 lymphocyte count and ART use in order to identify possible risk factors for hyper homocysteinemia in HIV population.&#x0D; Method: Employing a cross sectional design; we compared mean plasma levels of homocysteine, full blood count parameters and CD4+ lymphocytes counts in HIV positive patients and HIV negative controls. One hundred and twenty patients with HIV infection attending the APIN clinic at the University College Hospital Ibadan and St Mary’s Catholic Hospital Eleta Ibadan and one hundred and twenty-six HIV negative healthy controls were compared in the study.&#x0D; Results: Fifty-nine point one percent of the HIV positive patient had hyperhomocysteinemia i.e. homocysteine levels of &gt;18µmol/l. The mean plasma homocysteine levels were significantly higher at 24.4µmol/l (SD=13.8) (CI -2 to -8; p=0.002) in the HIV positive group compared with 19.5µmol/L (SD=10.6) in the control group. The use of Anti-retroviral drugs was not associated with higher homocysteine level in the seropositive group and neither were factors like age, gender or the use of combined oral contraceptive pills. There was no correlation between CD4 cell count and homocysteine levels (r= -0.01; p=0.9).&#x0D; Conclusion: Homocysteine levels are elevated in HIV positive patients and hyperhomocysteinemia was found in a significant number of HIV positive patients. None of the patients investigated had features of thromboembolism or outright deep venous thrombosis. Neither CD4 cell counts nor traditional risk factors were associated with the higher homocysteine levels.

Combinational effect of angiotensin receptor blocker and folic acid therapy on uric acid and creatinine level in hyperhomocysteinemia-associated hypertension.

Homocysteine [HSCH2 CH2 CH(NH2 )COOH] (Hcy) is a sulfur-containing amino acid of 135.18 Da of molecular weight, generated during conversion of methionine to cysteine. If there is a higher accumulation of Hcy in the blood, that is usually above 15µmol/L, it leads to a condition referred to as hyperhomocysteinemia. A meta-analysis of observational study suggested an elevated concentration of Hcy in blood, which is termed as the risk factors leading to ischemic heart disease and stroke. Further experimental studies stated that Hcy can lead to an increase in the proliferation of vascular smooth muscle cells and functional impairment of endothelial cells. The analyses confirmed some of the predictors for Hcy presence, such as serumuric acid (UA), systolic blood pressure, and hematocrit. However, angiotensin-converting enzyme inhibitors angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) alone are inadequate for controlling UA and creatinine level, although the addition of folic acid may be beneficial in hypertensive patients who are known to have a high prevalence of elevated Hcy. We hypothesized that combination therapy with an ARB (olmesartan) and folic acid is a promising treatment for lowering the UA and creatinine level in hyperhomocysteinemia-associated hypertension.

Plasma Cystathionine and Risk of Incident Stroke in Patients With Suspected Stable Angina Pectoris.

BackgroundCystathionine is an intermediate product in the transsulfuration pathway and formed during the B6‐dependent conversion of methionine to cysteine. Elevated plasma cystathionine has been related to atherosclerosis, which is a major etiological factor for ischemic stroke. However, the role of cystathionine in stroke development is unknown. Therefore, we prospectively assessed the association of circulating levels of cystathionine with risk of total and ischemic stroke.Methods and ResultsTwo‐thousand thirty‐six patients (64% men; median age, 62 years) undergoing coronary angiography for suspected stable angina pectoris were included. Stroke cases were identified by linkage to the CVDNOR (Cardiovascular Disease in Norway) project. Hazard ratios with confidence intervals (95% confidence interval) were estimated by using Cox‐regression analyses. During 7.3 years of median follow‐up, 124 (6.1%) incident strokes were ascertained, which comprised 100 cases of ischemic stroke. There was a positive association of plasma cystathionine with risk of total stroke and ischemic stroke. Comparing the fourth versus the first cystathionine quartiles, age‐ and sex‐adjusted hazard ratios (95% confidence interval) were 2.11 (1.19–3.75) and 2.56 (1.31–4.99) for total and ischemic stroke, respectively. Additional adjustment for major stroke risk factors only slightly attenuated the associations, which tended to be stronger in patients without previous or existing atrial fibrillation at baseline (hazard ratio [95% confidence interval], 2.43 [1.27–4.65] and 2.88 [1.39–5.98] for total and ischemic stroke, respectively).ConclusionsIn patients with suspected stable angina pectoris, plasma cystathionine was independently related to increased risk of total stroke and, in particular, ischemic stroke.Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT00354081.

Kinetics and Mechanism of Oxidative Conversion of Methionine to Sulfone by Chloramine-B in Acid Medium

Background: Methionine, Met, is one of the sulfur containing amino acids required in the human body by certain biochemical reactions. Since Met is not biosynthesized in humans, it needs to be supplied externally in diet. Met is highly susceptible to oxidation. Objective: The oxidation of Met to its sulfone by CAB in aqueous perchloric acid medium at 323 K has been kinetically studied. Method: Effect of varying ionic strength, solvent composition, dielectric constant has been determined. Effect of reduction product of Chloramine-B (CAB), benzenesulfonamide, on the reaction rate has also been investigated. Conclusion: The experimental rate law obtained is: rate = k׀ [CAB] [H2O]. Activation parameters have been evaluated using Arrhenius and Eyring plots. A mechanism consistent with the observed kinetic data has been discussed. A rate law has been derived based on the mechanism. Keywords: Chloramine-B, kinetics, mechanism, methionine, oxidation, rate law, reduction, sulfone.

A methionine-R-sulfoxide reductase, OsMSRB5, is required for rice defense against copper toxicity

Methionine sulfoxide reductases (MSRs), a family of enzymes catalyzing the conversion of methionine from its oxidized form into its reduced form, has a pivotal role in responding to oxidative stress. In the present study, we found that OsMSRB5 plays a crucial role in rice adaption to Cu stress. OsMSRB5 was mainly expressed in leaves, with low transcriptional levels of OsMSRB5 observed in seeds, stems, and roots; this gene was also induced by the excess copper (Cu) treatment. The functions of OsMSRB5 were analyzed through ectopic expression in Escherichia coli and functional disruption in rice. An in vitro enzymatic activity assay showed that OsMSRB5 had the ability to reduce free methionine-R-sulfoxide (Met-R-SO) and protein-bound-like Met-SO (dabsyl-Met-SO) to Met and dabsyl-Met, respectively. Ectopic expression of OsMSRB5 conferred E. coli cells higher tolerance to excess Cu and methyl viologen (MV). Furthermore, OsMSRB5 mutation decreased Cu and MV tolerance in rice. Our results demonstrate that rice OsMSRB5 is a functional methionine sulfoxide reductase and is involved in defense against Cu toxicity. In addition, rice seedlings responding to MV-induced oxidative stress showed a similar phenotype with excess Cu.

Methionine is required for cAMP-PKA-mediated morphogenesis and virulence of Candida albicans.

Candida albicans is a major human fungal pathogen, causing superficial, as well as life-threatening invasive infections. Therefore, it has to adequately sense and respond to the host defense by expressing appropriate virulence attributes. The most important virulence factor of C. albicans is the yeast-to-hyphae morphogenetic switch, which can be induced by numerous environmental cues, including the amino acid methionine. Here, we show an essential role for methionine permease Mup1 in methionine-induced morphogenesis, biofilm formation, survival inside macrophages and virulence. Furthermore, we demonstrate that this process requires conversion of methionine into S-adenosyl methionine (SAM) and its decarboxylation by Spe2. The resulting amino-propyl group is then used for biosynthesis of polyamines, which have been shown to activate adenylate cyclase. Inhibition of the SPE2 SAM decarboxylase gene strongly impairs methionine-induced morphogenesis on specific media and significantly delays virulence in the mouse systemic infection model system. Further proof of the connection between methionine uptake and initial metabolism and the cAMP-PKA pathway was obtained by showing that both Mup1 and Spe2 are required for cAMP production in response to methionine. Our results suggest that amino acid transport and further metabolism are interesting therapeutic targets as inhibitors of this may prevent the morphogenetic switch, thereby preventing virulence.

Mammalian Sulfur Amino Acid Metabolism: A Nexus Between Redox Regulation, Nutrition, Epigenetics, and Detoxification.

Transsulfuration allows conversion of methionine into cysteine using homocysteine (Hcy) as an intermediate. This pathway produces S-adenosylmethionine (AdoMet), a key metabolite for cell function, and provides 50% of the cysteine needed for hepatic glutathione synthesis. The route requires the intake of essential nutrients (e.g., methionine and vitamins) and is regulated by their availability. Transsulfuration presents multiple interconnections with epigenetics, adenosine triphosphate (ATP), and glutathione synthesis, polyol and pentose phosphate pathways, and detoxification that rely mostly in the exchange of substrates or products. Major hepatic diseases, rare diseases, and sensorineural disorders, among others that concur with oxidative stress, present impaired transsulfuration. Recent Advances: In contrast to the classical view, a nuclear branch of the pathway, potentiated under oxidative stress, is emerging. Several transsulfuration proteins regulate gene expression, suggesting moonlighting activities. In addition, abnormalities in Hcy metabolism link nutrition and hearing loss. Knowledge about the crossregulation between pathways is mostly limited to the hepatic availability/removal of substrates and inhibitors. However, advances regarding protein-protein interactions involving oncogenes, identification of several post-translational modifications (PTMs), and putative moonlighting activities expand the potential impact of transsulfuration beyond methylations and Hcy. Increasing the knowledge on transsulfuration outside the liver, understanding the protein-protein interaction networks involving these enzymes, the functional role of their PTMs, or the mechanisms controlling their nucleocytoplasmic shuttling may provide further insights into the pathophysiological implications of this pathway, allowing design of new therapeutic interventions. Antioxid. Redox Signal. 29, 408-452.