Enzymes Of Purine Metabolism Research Articles

The Prospective Effect of Allopurinol on the Oxidative Stress Index and Endothelial Dysfunction in Covid-19.

SARS-CoV-2 by the direct cytopathic effect or indirectly through the propagation of pro-inflammatory cytokines could cause endothelial dysfunction (ED) and oxidative stress (OS). It has been reported that OS is triggered by various types of viral infections, including SARS-CoV-2. Into the bargain, allopurinol is regarded as a potent antioxidant that acts through inhibition of xanthine oxidase (XO), which is an essential enzyme of purine metabolism. Herein, the present study aimed to find the potential protective effects of allopurinol on the biomarkers of OS and ED in patients with severe Covid-19. This single-center cohort study recruited 39 patients with mild-moderate Covid-19 compared with 41 patients with severe Covid-19. Nineteen patients with severe Covid-19 were on the allopurinol treatment because of underlying chronic gout 3 years ago compared with 22 Covid-19 patients not on this treatment. The recruited patients were allocated into three groups: group I, mild-moderate Covid-19 on the standard therapy (n = 39); group II, severe Covid-19 patients on the standard therapy only (n = 22); and group III, severe Covid-19 patients on the standard therapy plus allopurinol (n = 19). The duration of the study was 3 weeks from the time of hospitalization till the time of recovery. In addition, inflammatory biomarkers (D-dimer, LDH, ferritin, CRP, procalcitonin), neutrophil–lymphocyte ratio (NLR), endothelin-1 (ET-1), uric acid and oxidative stress index (OSI), CT scan score, and clinical score were evaluated at the time of admission and discharge regarding the effect of allopurinol treatment adds to the standard treatment of Covid-19. Allopurinol plus standard treatment reduced LDH, ferritin, CRP, procalcitonin, and ET-1 serum level significantly (P < 0.05) compared with Covid-19 patients on standard treatment. Besides, neutrophil (%), lymphocyte (%), and neutrophil–lymphocyte ratio (NLR) were reduced in patients with severe Covid-19 on standard treatment plus allopurinol compared with Covid-19 patients on standard treatment alone (P < 0.01). OSI was higher in patients with severe Covid-19 than mild-moderate Covid-19 patients (P = 0.00001) at admission. At the time of discharge, the oxidative status of Covid-19 patients was significantly improved compared with that at admission (P = 0.01). In conclusion, Covid-19 severity is linked with high OS and inflammatory reaction with ED development. High uric acid in patients with severe Covid-19 is correlated with high OS and inflammatory biomarkers. Allopurinol with standard treatment in patients with severe Covid-19 reduced oxidative and inflammatory disorders with significant amelioration of ED and clinical outcomes.

IMPDH dysregulation in disease: a mini review.

Inosine-5′-monophosphate dehydrogenase (IMPDH) is a highly conserved enzyme in purine metabolism that is tightly regulated on multiple levels. IMPDH has a critical role in purine biosynthesis, where it regulates flux at the branch point between adenine and guanine nucleotide synthesis, but it also has a role in transcription regulation and other moonlighting functions have been described. Vertebrates have two isoforms, IMPDH1 and IMPDH2, and point mutations in each are linked to human disease. Mutations in IMPDH2 in humans are associated with neurodevelopmental disease, but the effects of mutations at the enzyme level have not yet been characterized. Mutations in IMPDH1 lead to retinal degeneration in humans, and recent studies have characterized how they cause functional defects in regulation. IMPDH1 is expressed as two unique splice variants in the retina, a tissue with very high and specific demands for purine nucleotides. Recent studies have revealed functional differences among splice variants, demonstrating that retinal variants up-regulate guanine nucleotide synthesis by reducing sensitivity to feedback inhibition by downstream products. A better understanding of the role of IMPDH1 in the retina and the characterization of an animal disease model will be critical for determining the molecular mechanism of IMPDH1-associated blindness.

Connecting rapid promoting vibrations to conformational transitions in human purine nucleoside phosphorylase

One pathway to understanding the process by which enzymes catalyze chemical reactions is through the examination of internal correlated motions. There have been numerous studies that show these correlated motions may assist in catalysis, protein folding, and substrate specificity. It is also known through transition path sampling studies that rapid promoting vibrations contribute to enzyme catalysis. Human PNP is an important enzyme in purine metabolism, and it is the only purine salvage enzyme that catalyzes the reversible phosphorolysis of 6-oxopurine nucleosides to from a-D-ribose-1-phosphate.

Adenosine deaminase gene variant in diabetes and obesity.

Personal medicine is a new notion for individualizing treatment in the future. Studying pathogenic markers including genetic variants would be beneficial in better diagnosis and management of complex diseases such as diabetes and obesity. Adenosine deaminase (ADA) is a purine metabolic enzyme and modulates insulin activity in various tissues through several different mechanisms. Increased ADA activity is associated with decreased glucose uptake. A significant increase in serum deaminase activity has been reported in patients with T2DM and obesity. ADA gene polymorphisms seem to affect ADA enzymatic activity and a polymorphism at the position 4223 in the first intron of ADA gene (ADA 4223 A/C) has been previously associated with obesity. The aim of this study was to explore ADA gene 4223 A/C polymorphism and its association with obesity in patients with Type 2 diabetes. Obese patients (N = 133: 64 diabetic +69 non-diabetic) with BMI ≥ 30 and subjects with BMI < 30 (N = 152: 83 diabetics +69 non-diabetic) were recruited into a case-control association study. Blood samples were collected and after DNA extraction, the allele and genotype frequency for ADA gene polymorphism was determined using PCR-RFLP technique. We observed a significant increase for the frequency of AA+CA genotype in non-obese patients with diabetes compared to obese patients with diabetes (P = 0.04, OR = 2.1, 95%CI; 0.93-4.9). The higher frequency of AA+CA genotype in none obese diabetes individuals and lower frequency of this genotype in obese diabetes subjects indicates an important role for ADA gene polymorphism in diabetes subjects without obesity.

Clinico-radiological features, molecular spectrum, and identification of prognostic factors in developmental and epileptic encephalopathy due to inosine triphosphate pyrophosphatase (ITPase) deficiency.

Developmental and epileptic encephalopathy 35 (DEE 35) is a severe neurological condition caused by biallelic variants in ITPA, encoding inosine triphosphate pyrophosphatase, an essential enzyme in purine metabolism. We delineate the genotypic and phenotypic spectrum of DEE 35, analyzing possible predictors for adverse clinical outcomes. We investigated a cohort of 28 new patients and reviewed previously described cases, providing a comprehensive characterization of 40 subjects. Exome sequencing was performed to identify underlying ITPA pathogenic variants. Brain MRI (magnetic resonance imaging) scans were systematically analyzed to delineate the neuroradiological spectrum. Survival curves according to the Kaplan–Meier method and log‐rank test were used to investigate outcome predictors in different subgroups of patients. We identified 18 distinct ITPA pathogenic variants, including 14 novel variants, and two deletions. All subjects showed profound developmental delay, microcephaly, and refractory epilepsy followed by neurodevelopmental regression. Brain MRI revision revealed a recurrent pattern of delayed myelination and restricted diffusion of early myelinating structures. Congenital microcephaly and cardiac involvement were statistically significant novel clinical predictors of adverse outcomes. We refined the molecular, clinical, and neuroradiological characterization of ITPase deficiency, and identified new clinical predictors which may have a potentially important impact on diagnosis, counseling, and follow‐up of affected individuals.

Adenosine deaminase and cytokines associated with infectious diseases as risk factors for inflammatory arthritis and methotrexate as a potential prophylactic agent

Rheumatoid arthritis (RA), is an autoimmune disease resulting in inflamed joints with erosions and deformities. A complex interaction of genetic factors concomitant with a specific immune response against a variety of environmental factors might play a pivotal role in determining susceptibility to RA. RA is known to have infections as trigger points to develop autoimmunity and antibodies prior to the presentation of symptoms clinically. Infections beckon both the innate and the adaptive immune systems. The inflammatory cells such as macrophages and lymphocytes secrete Adenosine deaminase (ADA), an important enzyme in purine metabolism, which through deamination converts the extracellular adenosine to inosine causing a dip in adenosine levels and shifting the immune balance towards pro-inflammatory response. ADA induces production of inflammatory cytokines such as tumor necrosis factor alpha (TNFα), transforming growth factor beta (TGFβ), and interferon gamma (IFNγ). Infections parse as well as ADA activity can also lead to citrullination (deamination) which enhances auto-antibody production and can lead to systemic inflammation prior to the clinical symptoms of RA. So, the conversion of arginine to citrulline by peptidyl arginine deiminase enzyme (PAD) may be an important precursor to the development of RA. These antibody titers are maintained by ADA even after post infection by keeping the pro-inflammatory bias making it a chronic condition in RA. This eventually leads to joint erosions by enhanced osteoclastic activity, cartilage degradation, synoviocyte proliferation and reduced differentiation of osteoblasts from mesenchymal stem cells and also their mineralization. Methotrexate, a disease-modifying antirheumatic drug (DMARD) used for RA treatment can be used as a prophylactic agent to prevent the patients of high ADA activity, elevated cytokines and high anti-CCP antibodies titers from developing RA.

Understanding the mode of inhibition and molecular interaction of taxifolin with human adenosine deaminase

Adenosine deaminase is a zinc+2 dependent key enzyme of purine metabolism which irreversibly converts adenosine to inosine and form ammonia. Overexpression of adenosine deaminase has been linked to a variety of pathophysiological conditions such as atherosclerosis, hypertension, and diabetes. In the case of a cell-mediated immune response, ADA is thought to be a marker, particularly in type II diabetes. Deoxycoformycin is the most potent ADA inhibitor that has been discovered so far, but it has several drawbacks, including being toxic and having poor pharmacokinetics. Taxifolin, a flavonoid derived from plants, was discovered to be a potent inhibitor of the human ADA (hADA) enzyme in the current study. Taxifolin bound at the active site of human ADA and showed fifty percent inhibition at a concentration of 400 µM against the enzyme. To better understand the interactions between taxifolin and human ADA, docking and molecular dynamic simulations were performed. In-silico studies using autodock revealed that taxifolin bound in the active site of human ADA with a binding energy of −7.4 kcal mol −1 and a theoretical Ki of 3.7 uM. Comparative analysis indicated that taxifolin and deoxycoformycin share a common binding space in the active site of human ADA and inhibit its catalytic activity similarly. The work emphasises the need of employing taxifolin as a lead chemical in order to produce a more precise and effective inhibitor of the human ADA enzyme with therapeutic potential. Communicated by Ramaswamy H. Sarma

Метаболічні фактори, що визначають ефективність гіпоурикемічного лікування подагричного артриту

Актуальність. На сьогодні лікування деяких форм артикулярної патології при подагрі залишається недостатньо ефективним, а досягнення нормальних значень показників урикемії на тлі застосування уратнормалізуючих медикаментозних препаратів досить часто відсутнє. Мета дослідження: оцінити ступінь впливу початкових параметрів пуринового метаболізму і молекул середньої маси (МСМ) різних фракцій на ефективність урикодепресивної й урикозуричної терапії подагричного артриту. Матеріали та методи. Під спостереженням перебували 105 хворих на первинну подагру, серед яких було 92 % чоловіків і 8 % жінок віком 26–76 років. Перед початком лікування в сироватці крові вивчали вміст чинників пуринового метаболізму (сечової кислоти (AU), оксипуринолу (ОР), аденіну, гуаніну, ксантину, гіпоксантину, ксантиноксидази, ксантиндезамінази, аденозиндезамінази, 5-нуклеотидази, молібдену, свинцю), а також МСМ різних фракцій (амінопептидної (АФ), пептидної (ПФ), нуклеотидної (НФ), хроматофорної (ХФ)) та інтегрального середньомолекулярного індексу. Використовували спектрофотометр СФ46, біо­аналізатор Olympus-AU640 і атомно-абсорбційний спектрометр з електрографітовим атомізатором SolAAr-Mk2-MOZe. Ефективність лікування оцінювали за 3–5 тижнів. Результати. У 27 % випадків констатовано незначне поліпшення, у 68 % — поліпшення, у 8 % — значне поліпшення. Первинна подагра перебігає з порушеннями метаболізму AU, ОР, пуринових основ, ферментів обміну пуринів і пуринасоційованих мікроелементів, інтегральні зміни яких залежать від форми суглобового синдрому, наявності периферійних і кісткових тофусів, визначають кістково-деструктивні артикулярні ушкодження, при цьому прогнознегативним чинником щодо тяжкості артропатії є високий рівень в крові пуринових основ. При подагрі вірогідно зростають в крові концентрації АФ, ПФ, НФ, ХФ і СМІ, при цьому вміст АФ тісно пов’язаний з тяжкістю перебігу суглобового синдрому, визначає ступінь звуження суглобових щілин і субхондрального склерозу, розвиток остеоузур і змін менісків, а показники МСМ різних фракцій мають кореляційний зв’язок з параметрами пуринового метаболізму. Значне поліпшення й поліпшення в процесі патогенетичної терапії спостерігається у 3/4 від числа хворих, що щільно пов’язане з формою артриту, наявністю тофусов і внутрішньосуглобових тіл Гоффа, а також з типом гіперурикемії, залежить від використання в комплексі лікувальних заходів фебуксостату, статинів і фібратів, визначається початковим станом пуринового обміну, рівнями МСМ фракцій НФ і ХФ. Висновки. Вивчені метаболічні чинники не лише беруть участь в патогенезі подагричного артриту, але й впливають на ефективність уриконормалізуючих препаратів.

Overexpression of Phosphoribosyl Pyrophosphate Synthase Enhances Resistance of Chlamydomonas to Ionizing Radiation.

The enzyme phosphoribosyl pyrophosphate synthase (PRPS) catalyzes the conversion of ribose 5-phosphate into phosphoribosyl diphosphate; the latter is a precursor of purine and pyrimidine nucleotides. Here, we investigated the function of PRPS from the single-celled green alga Chlamydomonas reinhardtii in its response to DNA damage from gamma radiation or the alkylating agent LiCl. CrPRPS transcripts were upregulated in cells treated with these agents. We generated CrPRPS-overexpressing transgenic lines to study the function of CrPRPS. When grown in culture with LiCl or exposed to gamma radiation, the transgenic cells grew faster and had a greater survival rate than wild-type cells. CrPRPS overexpression enhanced expression of genes associated with DNA damage response, namely RAD51, RAD1, and LIG1. We observed, from transcriptome analysis, upregulation of genes that code for key enzymes in purine metabolism, namely ribonucleoside-diphosphate pyrophosphokinase subunit M1, adenylate kinase, and nucleoside-diphosphate kinase. We conclude that CrPRPS may affect DNA repair process via regulation of de novo nucleotide synthesis.

IMPDH2 and HPRT expression and a prognostic significance in preoperative and postoperative patients with osteosarcoma

Osteosarcoma is one of the most aggressive bone tumors in children and adolescents. Development of effective therapeutic options is still lacking due to the complexity of the genomic background. In previous work, we applied a proteomics-guided drug repurposing to explore potential treatments for osteosarcoma. Our follow-up study revealed an FDA-approved immunosuppressant drug, mycophenolate mofetil (MMF) targeting inosine-5′-phosphate dehydrogenase (IMPDH) enzymes, has an anti-tumor effect that appeared promising for further investigation and clinical trials. Profiling of IMPDH2 and hypoxanthine–guanine phosphoribosyltransferase (HPRT), key purine-metabolizing enzymes, could deepen understanding of the importance of purine metabolism in osteosarcoma and provide evidence for expanded use of MMF in the clinic. In the present study, we investigated levels of IMPDH2, and HPRT in biopsy of 127 cases and post-chemotherapy tissues in 20 cases of high-grade osteosarcoma patients using immunohistochemical (IHC) analysis. Cox regression analyses were performed to determine prognostic significance of all enzymes. The results indicated that low levels of HPRT were significantly associated with a high Enneking stage (P = 0.023) and metastatic status (P = 0.024). Univariate and multivariate analyses revealed that patients with low HPRT expression have shorter overall survival times [HR 1.70 (1.01–2.84), P = 0.044]. Furthermore, high IMPDH2/HPRT ratios were similarly associated with shorter overall survival times [HR 1.67 (1.02–2.72), P = 0.039]. Levels of the enzymes were also examined in post-chemotherapy tissues. The results showed that high IMPDH2 expression was associated with shorter metastasis-free survival [HR 7.42 (1.22–45.06), P = 0.030]. These results suggest a prognostic value of expression patterns of purine-metabolizing enzymes for the pre- and post-chemotherapy period of osteosarcoma treatment.

Structural and activity changes of xanthine oxidase induced by cetyltrimethylammonium bromide and its Gemini homologue bis(cetyldimethylammonium)hexane dibromide: a comparative study

Interaction of xanthine oxidase (XOD), a key enzyme in purine metabolism, with cetyltrimethylammonium bromide (CTAB) and bis(cetyldimethylammonium)hexane dibromide (C16C6C16Br2) has been studied by employing different techniques at pH 7.4 and 25 °C. The existence of interaction between the surfactants and the enzyme was established by the deviation of tensiometric profiles of surfactants with and without the enzyme. The results obtained by Circular Dichroism, Fluorescence and activity suggest that the Gemini surfactant interacts strongly with the XOD than its conventional homologue. The peculiar structural design of C16C6C16Br2, enhanced ability for electrostatic and hydrophobic interactions, and unique aggregation behavior is accountable for the effectiveness of the Gemini in interacting/unfolding the XOD. The results are contemplated to offer valuable understandings in designing the surfactant-based formulations to moderate the activity of XOD.

Tissue xanthine oxidoreductase activity in a mouse model of aristolochic acid nephropathy.

Xanthine oxidoreductase (XOR) is a critical enzyme in purine metabolism and uric acid production, and its levels are reported to increase during stress, thereby promoting organ damage. Herein, we investigated the activity of XOR in a mouse model of aristolochic acid I (AA)‐induced nephropathy, a type of nephrotoxic chronic kidney disease (CKD). A persistent decrease in renal function was observed in mice up to 4 weeks after 4 weeks of AA (2.5 mg kg−1) administration. Renal histology revealed an increase in tubular interstitial fibrosis over time. Although AA administration did not change XOR activity in the plasma, heart, liver, or muscle, XOR activity was persistently increased in renal tissue. Our results suggest that the renal tissue‐specific increase in XOR activity is involved in the progression of tubulo‐interstitial disorders, specifically fibrosis.

Bovine milk exosomes attenuate the alteration of purine metabolism and energy status in IEC-6 cells induced by hydrogen peroxide

Evidence suggests that dietary depletion of bovine milk exosomes and their cargos causes a loss of circulating microRNAs and a series of health problems. The aim of the current study was to determine whether bovine milk exosomes affect purine nucleotide metabolism and energy metabolism in oxidatively stressed intestinal crypt epithelial cells (IEC-6). Cells were pretreated with exosomes, followed by H2O2 to induce oxidative stress. Reactive oxidative species (ROS) levels, purine nucleotides, purine metabolic key enzyme activities, cell energy status, and AMPK protein expression were analysed. Exosome pretreatment reduced ROS level and the activities of adenosine deaminase and xanthine oxidase induced by H2O2 in cells. Total adenine nucleotides and energy charge were increased with exosome pretreatment, while the AMPK phosphorylation level was downregulated. The results indicated that bovine milk exosomes could attenuate purine nucleotide catabolism and improve energy status in oxidatively stressed IEC-6 cells and exerted protective effects against oxidative stress.

Greater coronary lipid core plaque assessed by near-infrared spectroscopy intravascular ultrasound in patients with elevated xanthine oxidoreductase: a mechanistic insight.

Elevated serum uric acid level was reportedly associated with greater coronary lipid plaque. Xanthine oxidoreductase (XOR) is a rate-limiting enzyme in purine metabolism and believed to play an important role in coronary atherosclerosis. However, the relation of XOR to coronary lipid plaque and its mechanism are unclear. Patients with stable coronary artery disease undergoing elective percutaneous coronary intervention under near-infrared spectroscopy intravascular ultrasound (NIRS-IVUS) guidance were prospectively enrolled. They were divided into three groups according to serum XOR activities: low, normal, and high. Coronary lipid core plaques in non-target vessels were evaluated by NIRS-IVUS with lipid core burden index (LCBI) and a maximum LCBI in 4mm (maxLCBI4mm). Systemic endothelial function and inflammation were assessed with reactive hyperemia index (RHI) and high-sensitivity C-reactive protein, neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratio. Of 68 patients, 26, 31, and 11 were classified as low, normal, and high XOR activity groups. LCBI (474.4 ± 171.6 vs. 347.4 ± 181.6 vs. 294.0 ± 155.9, p = 0.04) and maxLCBI4mm (102.1 ± 56.5 vs. 65.6 ± 48.5 vs. 55.6 ± 37.8, p = 0.04) were significantly higher in high XOR group than in normal and low XOR groups. Although RHI was significantly correlated with body mass index, diabetes, current smoking, and high-density lipoprotein cholesterol, no relation was found between XOR activity and RHI. There were also no relations between XOR activity and C-reactive protein, neutrophil-to-lymphocyte ratio, or platelet-to-lymphocyte ratio. In conclusion, elevated XOR activity was associated with greater coronary lipid core plaque in patients with stable coronary artery disease, without significant relations to systemic endothelial function and inflammation.

Greater coronary lipid core plaque assessed by near-infrared spectroscopy intravascular ultrasound in patients with elevated xanthine oxidoreductase: a mechanistic insight

Abstract Background Elevated serum uric acid level was reportedly associated with greater coronary lipid plaque. Xanthine oxidoreductase (XOR) is a rate-limiting enzyme in purine metabolism and believed to play important roles in coronary atherosclerosis. However, the relation of XOR to coronary lipid plaque and its mechanism are unclear. Purpose The aim of this study was to assess the impact of XOR on coronary lipid plaque and the associated factors with XOR in coronary artery disease (CAD). Methods Patients with stable CAD undergoing elective percutaneous coronary intervention under near-infrared spectroscopy intravascular ultrasound (NIRS-IVUS) guidance were prospectively enrolled. They were divided into three groups according to serum XOR activities; low, normal, and high. Coronary lipid core plaques in non-target vessels were evaluated by NIRS-IVUS with lipid core burden index (LCBI) and a maximum LCBI in 4 mm (maxLCBI4mm). Systemic endothelial function and inflammation were assessed with reactive hyperemia index (RHI) and high-sensitivity C-reactive protein, neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratio. Results Of 68 patients, 26, 31, and 11 were classified as low, normal, and high XOR activity groups. LCBI (474.4±171.6 vs. 347.4±181.6 vs. 294.0±155.9, p=0.04) and maxLCBI4mm (102.1±56.5 vs. 65.6±48.5 vs. 55.6±37.8, p=0.04) were significantly higher in high XOR group than in normal and low XOR groups. Although RHI was significantly correlated with body mass index, diabetes, current smoking, and high-density lipoprotein cholesterol, no relation was found between XOR activity and RHI (Figure). There were also no relations between XOR activity and high-sensitivity C-reactive protein, neutrophil-to-lymphocyte ratio, or platelet-to-lymphocyte ratio (Figure). Conclusion Elevated XOR activity was associated with greater coronary lipid plaque in patients with stable CAD, without significant relations to systemic endothelial function and inflammation. Funding Acknowledgement Type of funding source: None

Efficiency of Galanti and Guisti Method of ADA Estimation in Comparison with the Gold Standard.

Adenosine Deaminase, the key enzyme of purine metabolism catalyzing the irreversible hydrolytic deamination of adenosine to inosine is implicated in a varied spectrum of human diseases ranging from SCID to TB and pneumonia. Estimation of ADA offers an easy, relatively affordable and reliable diagnostic alternative and/ or adjunct (specially in a TB endemic nation) which emphasizes the necessity of a feasible and implementable alternative method to the Diazyme method of ADA estimation requiring high end autoanalyzer and infrastructural setup. Sixty body fluids samples (irrespective of gender, age, diagnosis or sample type) received by the Clinical Biochemistry Laboratory, Kasturba Medical College, Manipal for fluid ADA estimation by the Diazyme assay method (cobas 6000) was simultaneously processed by the Galanti and Guisti manual method to estimate the comparability and the aggregability of results obtained by the two analytical techniques. The Galanti and Guisti manual method of ADA estimation showed aggregability with the Diazyme autoanalyzer method for 90% of the assayed study samples with the manual method uniformly showing higher values when compared to the analyzer method. A correction factor of 2.44 was arrived at which could effectively achieve comparability between the two assay methods. The Galanti and Guisti manual method of ADA estimation might be a feasible, rapid, reliable and cost-effective method for estimation of fluid ADA when compared to the cost and infrastructure intensive autoanalyzer.

Therapeutic Perspectives of Adenosine Deaminase Inhibition in Cardiovascular Diseases

Adenosine deaminase (ADA) is an enzyme of purine metabolism that irreversibly converts adenosine to inosine or 2′deoxyadenosine to 2′deoxyinosine. ADA is active both inside the cell and on the cell surface where it was found to interact with membrane proteins, such as CD26 and adenosine receptors, forming ecto-ADA (eADA). In addition to adenosine uptake, the activity of eADA is an essential mechanism that terminates adenosine signaling. This is particularly important in cardiovascular system, where adenosine protects against endothelial dysfunction, vascular inflammation, or thrombosis. Besides enzymatic function, ADA protein mediates cell-to-cell interactions involved in lymphocyte co-stimulation or endothelial activation. Furthermore, alteration in ADA activity was demonstrated in many cardiovascular pathologies such as atherosclerosis, myocardial ischemia-reperfusion injury, hypertension, thrombosis, or diabetes. Modulation of ADA activity could be an important therapeutic target. This work provides a systematic review of ADA activity and anchoring inhibitors as well as summarizes the perspectives of their therapeutic use in cardiovascular pathologies associated with increased activity of ADA.

Activity of Several Purine Metabolic Enzymes in Sera of Pregnant Women

Activity of Several Purine Metabolic Enzymes in Sera of Pregnant Women

Fibroblast growth factor 2 upregulates ecto-5'-nucleotidase and adenosine deaminase via MAPK pathways in cultured rat spinal cord astrocytes.

Adenosine triphosphate (ATP) and adenosine are neurotransmitters and neuromodulators in the central nervous system. Astrocytes regulate extracellular concentration of purines via ATP release and its metabolisms via ecto-enzymes. The expression and activity of purine metabolic enzymes in astrocytes are increased under pathological conditions. We previously showed that fibroblast growth factor 2 (FGF2) upregulates the expression and activity of the enzymes ecto-5'-nucleotidase (CD73) and adenosine deaminase (ADA). Here, we further demonstrate that this occurs in concentration- and time-dependent manners in cultured rat spinal cord astrocytes and is suppressed by inhibitors of the FGF receptor as well as the mitogen-activated protein kinases (MAPKs). We also found that FGF2 increased the phosphorylation of MAPKs, including extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 MAPK, leading to the increased expression and activity of CD73 and ADA. Our findings reveal the involvement of FGF2/MAPK pathways in the regulation of purine metabolic enzymes in astrocytes. These pathways may contribute to the control of extracellular purine concentrations under physiological and pathological conditions.

Surveying purine biosynthesis across the domains of life unveils promising drug targets in pathogens.

Purines play an integral role in cellular processes such as energy metabolism, cell signaling and encoding the genetic makeup of all living organisms-ensuring that the purine metabolic pathway is maintained across all domains of life. To gain a deeper understanding of purine biosynthesis via the de novo biosynthetic pathway, the genes encoding purine metabolic enzymes from 35 archaean, 69 bacterial and 99 eukaryotic species were investigated. While the classic elements of the canonical purine metabolic pathway were utilized in all domains, a subset of familiar biochemical roles was found to be performed by unrelated proteins in some members of the Archaea and Bacteria. In the Bacteria, a major differentiating feature of de novo purine biosynthesis is the increasing prevalence of gene fusions, where two or more purine biosynthesis enzymes that perform consecutive biochemical functions in the pathway are encoded by a single gene. All species in the Eukaryota exhibited the most common fusions seen in the Bacteria, in addition to new gene fusions to potentially increase metabolic flux. This complexity is taken further in humans, where a reversible biomolecular assembly of enzymes known as the purinosome has been identified, allowing short-term regulation in response to metabolic cues while expanding on the benefits that can come from gene fusion. By surveying purine metabolism across all domains of life, we have identified important features of the purine biosynthetic pathway that can potentially be exploited as prospective drug targets.