End Product Of Purine Catabolism Research Articles

Unveiling overlooked pathways: The uric acid catabolism genes in the human genome

In hominids, including Homo sapiens, uric acid is the end product of purine catabolism. In contrast, other placental mammals further degrade uric acid to (S)-allantoin by enzymes such as urate oxidase (uricase), HIU hydrolase (HIUase), and OHCU decarboxylase. Some organisms, such as frogs and fish, hydrolyze (S)-allantoin to allantoate and eventually to (S)-ureidoglycolate and urea, while marine invertebrates convert urea to ammonium. In H. sapiens, mutations in the uricase gene led to a reduction in the selective pressure for maintaining the integrity of the genes encoding the other enzymes of the purine catabolism pathway, resulting in an accumulation of uric acid. The hyperuricemia resulting from this accumulation is associated with gout, cardiovascular disease, diabetes, and preeclampsia. Many commonly used drugs, such as aspirin, can also increase uric acid levels. Despite the apparent absence of these enzymes in H. sapiens, there appears to be production of transcripts for uricase (UOX), HIUase (URAHP), OHCU decarboxylase (URAD), and allantoicase (ALLC). While some URAHP transcripts are classified as long non-coding RNAs (lncRNAs), URAD and ALLC produce protein-coding transcripts. Given the presence of these transcripts in various tissues, we hypothesized that they may play a role in the regulation of purine catabolism and the pathogenesis of diseases associated with hyperuricemia. Here, we specifically investigate the unique aspects of purine catabolism in H. sapiens, the effects mutations of the uricase gene, and the potential regulatory role of the corresponding transcripts. These findings open new avenues for research and therapeutic approaches for the treatment of hyperuricemia and related diseases.

Cysteine Enrichment Mediates Co-Option of Uricase in Reptilian Skin and Transition to Uricotelism.

Uric acid is the main means of nitrogen excretion in uricotelic vertebrates (birds and reptiles) and the end product of purine catabolism in humans and a few other mammals. While uricase is inactivated in mammals unable to degrade urate, the presence of orthologous genes without inactivating mutations in avian and reptilian genomes is unexplained. Here we show that the Gallus gallus gene we name cysteine-rich urate oxidase (CRUOX) encodes a functional protein representing a unique case of cysteine enrichment in the evolution of vertebrate orthologous genes. CRUOX retains the ability to catalyze urate oxidation to hydrogen peroxide and 5-hydroxyisourate (HIU), albeit with a 100-fold reduced efficiency. However, differently from all uricases hitherto characterized, it can also facilitate urate regeneration from HIU, a catalytic property that we propose depends on its enrichment in cysteine residues. X-ray structural analysis highlights differences in the active site compared to known orthologs and suggests a mechanism for cysteine-mediated self-aggregation under H2O2-oxidative conditions. Cysteine enrichment was concurrent with the transition to uricotelism and a shift in gene expression from the liver to the skin where CRUOX is co-expressed with β-keratins. Therefore, the loss of urate degradation in amniotes has followed opposite evolutionary trajectories: while uricase has been eliminated by pseudogenization in some mammals, it has been repurposed as a redox-sensitive enzyme in the reptilian skin.

EFFECT OF MELINJO SEED EXTRACT ON URIC ACID LEVELS OF HYPERURICEMIC MALE WISTAR RATS

Background : Uric acid is the end product of purine catabolism carried out in the liver. Increased level of uric acid in blood is called hyperuricemia, which might cause gout if it is not treated properly. Melinjo (Gnetum gnemon L.) plant is a native plant of Indonesia that contains flavonoids and stilbenoid potential as antihyperuricemia. Aim : This paper aimed to study the effect of melinjo seed extract on uric acid levels. Methods : Thirty-six male wistar rats were randomly divided into 6 groups, consists of healthy control group, hyperuricemic control, Allopurinol control, and treatment groups (3 groups). Hyperuricemia was induced by the administration of block broth and potassium oxonate for 4 weeks. Melinjo seed extract doses of 250, 500, and 2000 mg/kg BW, and allopurinol 90 mg/kg BW was given orally for 2 weeks. Statistical analysis was conducted to evaluate differences among groups before and after the intervention. Results : Three doses could significantly reduce uric acid levels (p<0.05) from 5.61±0.95 to 2.45±1.21; 5.86±1.84 to 2.04±1.11; and 5.95±0.91 to 3.59±1.58, respectively. However, there is no significant difference between the three doses. The effectiveness of melinjo seed extract at a dose of 500 mg/kg BW reduced uric acid levels by 65%, a dose of 250 mg/kg BW by 56%, and allopurinol 90 mg/kg BW by 10%. Conlusion : Melinjo seed extract can reduce uric acid levels even though there is no effect of graded dose.

Bioactive Compounds in Garlic (Allium sativum) and Black Garlic as Antigout Agents, Using Computer Simulation.

Uric acid, which causes gout, is the end product of purine catabolism, synthesized by xanthine oxidase, guanine deaminase, adenine deaminase, purine nucleoside phosphorylase, and 5-nucleotidase II. Garlic contains bioactive compounds that have potential as antigout agents. Garlic fermentation to black garlic changes its components, which may affect its beneficial potential. This study aimed to select types of garlic (Indonesian garlic) and imported garlic, and to predict the interaction between their compounds and five target proteins through an in silico approach and a multivariate analysis, namely partial least squares-discriminant analysis (PLS-DA), to determine their different constituents. The target proteins were collected from open-access databases, and the compounds were identified using mass spectrometry data. The PLS-DA score plot succeeded in classifying the samples into three classes, with each class having a discriminatory compound. Based on the in silico studies, we predicted the best binding score of the five target proteins with seven important compounds: alliin, N-acetyl-S-allyl-L-cysteine, ajoene, pyridoxal, pyridoxamine, 4-guanidinobutyric acid, and D-glucosamine. These were mostly found in black garlic, with no different concentrations in the local and imported samples. Through this approach, we concluded that black garlic is a better candidate for antigout treatments, as several compounds were found to have good binding to the target proteins.

A Potential Regulatory Role of Xanthine Dehydrogenase (XDH) in the Kidney Development and Damage

There is a clear association of uric acid (UA) dysregulation in cardiovascular and chronic kidney diseases elucidated in the literature. Xanthine dehydrogenase (XDH) encodes for XDH enzyme that catalyzes hypoxanthine oxidation to xanthine and xanthine to UA, the end-product of purine catabolism in humans. UA can act as both an antioxidant scavenging reactive oxygen species (ROS) and conditionally a pro-oxidant. The lack of understanding of UA metabolism and its impact on CKD progression reflects the current controversy regarding the clinical management of the related pathologies. To explore mechanistic insights into UA affecting the kidney, we created a genetic ablation of the Xdh gene in the Dahl salt-sensitive rat background (SSXdh-/-). The absence of Xdh protein expression in SSXdh-/- was confirmed by Western blotting and immunohistochemistry analyses. The knockout rat is underdeveloped (179 ± 6 and 70 ± 7 g: N=9 for both male SSXdh+/+ and SSXdh-/-) and hypouricemic (UA in plasma below the level of detection). RNA-Seq analysis of kidney tissue of the SSXdh-/- and SSXdh+/+ 6-week-old rats revealed 4738 differentially expressed genes. The functional analyses of the obtained data were performed using the ingenuity pathway analysis (IPA) software. The changes in oxidative phosphorylation and the presence of mitochondrial dysfunction were among the top canonical pathways associated with the differentially expressed genes. The cardiac hypertrophy signaling pathway was enhanced the most (z-score 6.5). IPA toxic function analysis suggested the presence of renal damage. Among the upregulated genes were transforming growth factor-β (Tgf-β) and connective tissue growth factor (Ccn2), previously reported to drive the tissue fibrosis. Indeed, SSXdh-/- rats show increased levels of fibrosis in the kidneys. Western blot analysis revealed Ctgf lacking in the SSXdh-/- rats despite the increased mRNA levels. Ctgf is essential for kidney development, and the lack of this protein might explain the underdeveloped kidneys seen in the SSXdh-/- rat. Furthermore, we analyzed the expression of the primary transporters for UA in the kidney: Urat1 and Glut9, encoded by Slc22a12 and Slc2a9 genes, respectively. Western blot analysis revealed that Urat1 is not detectable and Glut9 expression is decreased in SSXdh-/- rats; potential glycosylation of Glut9 in SSXdh-/- rats is also observed. Catalase enzyme encoding Cat gene is also downregulated (log FC=-3.05) in SSXdh-/- rats, indicating the potential ROS production increase. These results provide insights into the regulatory role of the Xdh gene beyond purine catabolism that involves kidney tissue development and kidney damage.

The Role of Xanthine Dehydrogenase (XDH) and Uric Acid in the Kidney Development and Renal Injury

Uric acid is the end product of purine catabolism in humans and is capable of acting as both an antioxidant scavenging reactive oxygen species and conditionally a pro‐oxidant. Pathophysiological changes in serum uric acid levels (hyperuricemia and hypouricemia) are associated with prevalent diseases, including hypertension and chronic kidney disease as well as rare disorders, such as hereditary xanthinuria. Despite the clear association between uric acid dysregulation and pathology, the mechanisms involved remain unclear. XDH and xanthine oxidase (XO) (together known as Xanthine oxidoreductase (XOR)) is a complex enzyme group that catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid. To assess the role of this pathway beyond purine catabolism, we created a genetic ablation of the Xdh gene in the Dahl salt‐sensitive rat background (SSXdh−/−). Sequencing of SSXdh−/− genomic DNA confirmed a 7‐base‐pair‐deletion in exon 4 of the Xdh gene located on chromosome 6. The absence of Xdh protein expression in homozygotes and a reduction in heterozygotes was confirmed by both Western blot and immunohistochemistry analyses. SSXdh−/− rats exhibited early mortality with 7 out of 28 rats not surviving till 6 weeks of age compared to SSXdh+/− and SSXdh+/+ littermates, all of whom survived. Plasma uric acid of 6 weeks old male rats was 0.25±0.03 mg/dl (N=6) in SSXdh+/+ rats and decreased to a level out of the detectable range by the test in the SSXdh−/− group. The 24hr uric acid excretion was also dramatically decreased in SSXdh−/− rats compared to SSXdh+/+ littermates. Masson’s Trichrome staining revealed severe renal damage with an increase in fibrosis (1 and 14% (N=3 and 2 for male SSXdh+/+ and SSXdh−/−, respectively), and dilated tubules in the SSXdh−/− rats. Total body weight was decreased in SSXdh−/− rats, indicating a failure to thrive compared to control rats (190 ± 4 and 58 ± 8 g; N=6 and 4 for male SSXdh+/+ and SSXdh−/−). Additionally, In SSXdh−/− rats at 6 weeks, Western blot analysis showed a lack of connective tissue growth factor (CTGF), which is known to be critical in the nephrogenesis. No apparent sex‐specific differences in development or kidney injury were identified. Our results suggest that the genetic ablation of Xdh caused uric acid depletion and severe renal damage. Therefore, XOR may be essential for the development of the kidney and survival of the rats by regulating purine catabolism.Support or Funding InformationSupported by the Department of Veteran Affairs Grant I01 BX004024 and the National Institutes of Health Grants R35 HL‐135749.

Sugar-Induced Obesity and Insulin Resistance Are Uncoupled from Shortened Survival in Drosophila

SummaryHigh-sugar diets cause thirst, obesity, and metabolic dysregulation, leading to diseases including type 2 diabetes and shortened lifespan. However, the impact of obesity and water imbalance on health and survival is complex and difficult to disentangle. Here, we show that high sugar induces dehydration in adult Drosophila, and water supplementation fully rescues their lifespan. Conversely, the metabolic defects are water-independent, showing uncoupling between sugar-induced obesity and insulin resistance with reduced survival in vivo. High-sugar diets promote accumulation of uric acid, an end-product of purine catabolism, and the formation of renal stones, a process aggravated by dehydration and physiological acidification. Importantly, regulating uric acid production impacts on lifespan in a water-dependent manner. Furthermore, metabolomics analysis in a human cohort reveals that dietary sugar intake strongly predicts circulating purine levels. Our model explains the pathophysiology of high-sugar diets independently of obesity and insulin resistance and highlights purine metabolism as a pro-longevity target.

Relationship Between Serum Uric Acid Levels and Cognitive Functions in Bipolar Disorder

Objective: There are many studies showing that cognitive impairment persisted during the remission period in bipolar disorder type 1(BPD1). The end-product of purine catabolism, uric acid, is a natural antioxidant. The purinergic system has a role in the regulation of mood, sleep, energy, cognitive function, and behavior. Several studies have indicated that malfunctioning of the purinergic system might have an impact on the pathophysiology of BPD1. We aimed to compare differences in cognitive functions and serum urate levels between patients with BPD1and healthy controls (HC), and to evaluate the relationship between serum uric acid levels and cognitive functions in the patient group. Methods: This study included 75 euthymic patients with BPD1 and 75 healthy age- and sex-matched individuals. All participants completed a sociodemographic form, the Beck Anxiety Inventory (BAI), Beck Depression Inventory (BDI), and Montreal Cognitive Assessment Scale (MoCA), and underwent a neuropsychometric battery; blood serum uric acid levels were also measured. Clinical interviews for Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (SCID-I) and Young Mania Rating Scale (YMRS) scores were obtained for the patients; the HC group was investigated using the SCID non-patient version. Results: All of the neurocognitive domains, patients showed worse performance than healthy controls (p

Immobilization of Allantoinase for the Development of an Optical Biosensor of Oxidative Stress States.

Allantoin, the natural end product of purine catabolism in mammals, is non-enzymatically produced from the scavenging of reactive oxygen species through the degradation of uric acid. Levels of allantoin in biological fluids are sensitively influenced by the presence of free radicals, making this molecule a candidate marker of acute oxidative stress in clinical analyses. With this aim, we exploited allantoinase—the enzyme responsible for allantoin hydrolization in plants and lower organisms—for the development of a biosensor exploiting a fast enzymatic-chemical assay for allantoin quantification. Recombinant allantoinase was entrapped in a wet nanoporous silica gel matrix and its structural properties, function, and stability were characterized through fluorescence spectroscopy and circular dichroism measurements, and compared to the soluble enzyme. Physical immobilization in silica gel minimally influences the structure and the catalytic efficiency of entrapped allantoinase, which can be reused several times and stored for several months with good activity retention. These results, together with the relative ease of the sol-gel preparation and handling, make the encapsulated allantoinase a good candidate for the development of an allantoin biosensor.

Influence of muscle mass on the serum uric acid levels in children and adolescents

Background and aimUric acid (UA) is an end-product of purine catabolism and its increase in blood is a risk factor for several diseases. UA levels in men are usually higher than in women. This difference is partially due to sex hormones. We sought to investigate the onset of sexual difference in UA levels during pubertal development and the determinants of UA levels in children and adolescents. Methods and resultsThe muscle mass and fat mass were measured by multi-frequency bioelectrical impedance in a cross-sectional study involving 823 children and adolescents (both sexes; 6–18 years). Serum UA was determined using a commercially available kit. UA levels started to become higher in boys (5.0 ± 1.0 mg/dL) than in girls (4.1 ± 0.9 mg/dL) around 13 years. Boys in the highest quartile of muscle mass presented higher UA levels (5.2 ± 0.7 mg/dL) when compared with the third (4.2 ± 0.7 mg/dL), second (3.7 ± 0.9 mg/dL) and first (3.4 ± 0.9 mg/dL). Similarly, girls in the highest quartile of muscle mass presented higher UA levels (4.2 ± 0.7 mg/dL) when compared with the second (3.8 ± 0.9 mg/dL) and first (3.3 ± 0.9 mg/dL). Muscle mass explained 43.0% and 7.7% of the variability of UA in boys and girls, respectively. ConclusionSexual differences in serum UA levels begin at puberty and partially result from a direct influence of muscle mass.

Abstract 133: The Role of Xanthine Dehydrogenase ( XDH ) and Uric Acid in Renal Damage

Uric acid is the end product of purine catabolism in humans and is capable of acting as both an antioxidant scavenging reactive oxygen species and conditionally a pro-oxidant. Increased or decreased serum uric acid level (hyperuricemia or hypouricemia, respectively) are associated with a number of prevalent diseases including hypertension and chronic kidney disease as well as with rare disorders, such as primarily hereditary xanthinuria. Despite the clear association of uric acid dysregulation with pathophysiology, the mechanisms involved remain unclear. Xanthine oxidoreductase (XOR), XDH or xanthine oxidase (XO) is a complex metalloflavoenzyme that catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid. To assess the physiological and pathophysiological role of this pathway, we created a genetic ablation of Xdh gene in the Dahl salt-sensitive rat background (SS Xdh-/- ). Genomic DNA sequencing of the SS Xdh-/- rat model confirmed a 7-base-pair-deletion in exon 4 of the Xdh gene located on chromosome 6. SS Xdh-/- rats exhibited early mortality with 75% (21/28 rats) survival probability up to 45 days of age compared to SS Xdh+/- and SS Xdh+/+ littermates, all of whom survived. Plasma uric acid of 6 weeks old male rats was 0.27±0.03 mg/dl (N=3) and in SS Xdh+/+ rats decreased to a level out of the detectable range by the test in the SS Xdh-/- group. The uric acid/creatinine ratio in urine for SS Xdh+/+ rats was 0.27±0.01 (N=3) and extremely decreased for SS Xdh-/- rats (out of the range). In addition, the SS Xdh-/- rats showed severe renal damage with interstitial fibrosis and dilated tubules by Masson’s Trichrome staining. Kidney damage was further evident by the increased levels of albumin excretion in the SS Xdh-/- rats (1.21±0.28 (N=3) and 2.86±0.91 (N=6) for SS Xdh+/+ and SS Xdh-/- , respectively). The kidney weight / total body weight ratio was increased in SS Xdh-/- rats, indicating renal hypertrophy compared to control (10.97±0.2 (N=3) and 15.92±0.81 (N=5) for SS Xdh+/+ vs SS Xdh-/- rats). These results suggest that genetic ablation of Xdh caused uric acid depletion and severe renal damage. Xdh may be essential for the development of the kidney and survival of the rats by regulating purine catabolism.

Hubungan Obesitas dengan Kadar Asam Urat Darah pada Mahasiswa Program Studi Pendidikan Dokter Fakultas Kedokteran Universitas Sriwijaya

Uric acid is the end product of purine catabolism which is sinthesized especially by the liver and excreted through urinary tract. Increased blood uric acid levels can cause many disease such as gout arthritis, hipertension, and renal disease. Individual with obesity often have lower renal excretion rate and may have increased production of uric acid. This study is conducted to determine the relationship of obesity and blood uric acid levels.This Study with cross-sectional design took a sample of 119 students of Medical Education Program Study at Medical Faculty of the Sriwijaya University by consecutive sampling. Body weight, body height, and uric acid levels then are taken using measurement tools appropriate, categorized, and processed according to research objectivesThe study found that 27,5% female and 10,3% male have hyperuricemia. A total of 39,3% obese students and 16,5% non-obese students have high level of uric acid. The result of bivariate analysis showed that there is a significant relationship between obesity and gender with blood uric acid levels (p=0,022 and 0,035 respectively). After multivariate analysis, factor that has relationship with uric acid level is obesity.Obesity have a significant relationship with uric acid levels.

A de novo transcriptome of the Malpighian tubules in non-blood-fed and blood-fed Asian tiger mosquitoes Aedes albopictus: insights into diuresis, detoxification, and blood meal processing.

Background. In adult female mosquitoes, the renal (Malpighian) tubules play an important role in the post-prandial diuresis, which removes excess ions and water from the hemolymph of mosquitoes following a blood meal. After the post-prandial diuresis, the roles that Malpighian tubules play in the processing of blood meals are not well described.Methods. We used a combination of next-generation sequencing (paired-end RNA sequencing) and physiological/biochemical assays in adult female Asian tiger mosquitoes (Aedes albopictus) to generate molecular and functional insights into the Malpighian tubules and how they may contribute to blood meal processing (3–24 h after blood ingestion).Results/Discussion. Using RNA sequencing, we sequenced and assembled the first de novo transcriptome of Malpighian tubules from non-blood-fed (NBF) and blood-fed (BF) mosquitoes. We identified a total of 8,232 non-redundant transcripts. The Malpighian tubules of NBF mosquitoes were characterized by the expression of transcripts associated with active transepithelial fluid secretion/diuresis (e.g., ion transporters, water channels, V-type H+-ATPase subunits), xenobiotic detoxification (e.g., cytochrome P450 monoxygenases, glutathione S-transferases, ATP-binding cassette transporters), and purine metabolism (e.g., xanthine dehydrogenase). We also detected the expression of transcripts encoding sodium calcium exchangers, G protein coupled-receptors, and septate junctional proteins not previously described in mosquito Malpighian tubules. Within 24 h after a blood meal, transcripts associated with active transepithelial fluid secretion/diuresis exhibited a general downregulation, whereas those associated with xenobiotic detoxification and purine catabolism exhibited a general upregulation, suggesting a reinvestment of the Malpighian tubules’ molecular resources from diuresis to detoxification. Physiological and biochemical assays were conducted in mosquitoes and isolated Malpighian tubules, respectively, to confirm that the transcriptomic changes were associated with functional consequences. In particular, in vivo diuresis assays demonstrated that adult female mosquitoes have a reduced diuretic capacity within 24 h after a blood meal. Moreover, biochemical assays in isolated Malpighian tubules showed an increase in glutathione S-transferase activity and the accumulation of uric acid (an end product of purine catabolism) within 24 h after a blood meal. Our data provide new insights into the molecular physiology of Malpighian tubules in culicine mosquitoes and reveal potentially important molecular targets for the development of chemical and/or gene-silencing insecticides that would disrupt renal function in mosquitoes.

Serum uric acid and its relation to adenosine deaminase, lipid profile and oxidative stress in Diabetes Mellitus type 2

Aim/Background: Serum uric acid is an end product of purine catabolism. The relationship between the serum uric acid adenosine deaminase, lipid profile and oxidative stress in type 2 diabetes mellitus was studied to evaluate its role as one of the risk factor for coronary artery disease. Methods: The serum uric acid level in type 2 diabetes mellitus was compared with controls. The correlation between serum uric acid with adenosine deaminase (ADA), parameters of oxidative stress and serum lipids was also evaluated. Results: We observed serum uric acid level (5.74±0.49) mg/dl is significantly (p

Administration of Uric Acid in the Emergency Treatment of Acute Ischemic Stroke.

Oxidative stress is one of the main mechanisms implicated in the pathophysiology of inflammatory and neurodegenerative diseases of the central nervous system (CNS). Uric acid (UA) is the end product of purine catabolism in humans, and it is the main endogenous antioxidant in blood. Low circulating UA levels have been associated with an increased prevalence and worse clinical course of several neurodegenerative and inflammatory diseases of the CNS, including Parkinson's disease and multiple sclerosis. Moreover, the exogenous administration of UA exerts robust neuroprotective properties in experimental models of CNS disease, including brain ischemia, spinal cord injury, meningitis, and experimental allergic encephalitis. In experimental brain ischemia, exogenous UA and the thrombolytic agent alteplase exert additive neuroprotective effects when administered in combination. UA is rapidly consumed following acute ischemic stroke, and higher UA levels at stroke admission are associated with a better outcome and reduced infarct growth at follow-up. A recent phase II trial demonstrated that the combined intravenous administration of UA and alteplase is safe and prevents an early decrease of circulating UA levels in acute ischemic stroke patients. Moreover, UA prevents the increase in the circulating levels of the lipid peroxidation marker malondialdehyde and of active matrix metalloproteinase (MMP) 9, a marker of blood-brain barrier disruption. The moderately sized URICOICTUS phase 2b trial showed that the addition of UA to thrombolytic therapy resulted in a 6% absolute increase in the rate of excellent outcome at 90 days compared to placebo. The trial also showed that UA administration resulted in a significant increment of excellent outcome in patients with pretreatment hyperglycemia, in females and in patients with moderate strokes. Overall, the encouraging neuroprotective effects of UA therapy in acute ischemic stroke warrants further investigation in adequately powered clinical trials.

Allantoin and urate as suppressors of the genotoxic effect of 300–400 nm ultraviolet radiation

The genotoxicity of ultraviolet radiation with a wavelength of 300–400 nm (sunlight UVR) is mediated by the generation of reactive oxygen species (ROS). Research carried out on the basis of a bacterial model developed by us earlier indicated the existence of UV-protecting activity of allantoin, formed from uric acid in organisms of all vertebrates except human and anthropoid apes. Uric acid, which is the end product of purine catabolism in anthropoid apes, does not possess a statistically significant protective effect. The safety of allantoin makes it a promising component for sunscreens.

An aminotransferase branch point connects purine catabolism to amino acid recycling

Although amino acids are known precursors of purines, a pathway for the direct recycling of amino acids from purines has never been described at the molecular level. We provide NMR and crystallographic evidence that the PucG protein from Bacillus subtilis catalyzes the transamination between an unstable intermediate ((S)-ureidoglycine) and the end product of purine catabolism (glyoxylate) to yield oxalurate and glycine. This activity enables soil and gut bacteria to use the animal purine waste as a source of carbon and nitrogen. The reaction catalyzed by (S)-ureidoglycine-glyoxylate aminotransferase (UGXT) illustrates a transamination sequence in which the same substrate provides both the amino group donor and, via its spontaneous decay, the amino group acceptor. Structural comparison and mutational analysis suggest a molecular rationale for the functional divergence between UGXT and peroxisomal alanine-glyoxylate aminotransferase, a fundamental enzyme for glyoxylate detoxification in humans.

Allantoin and urate as the supressors of genotoxic effect of the ultraviolet irradiation with wavelength 300-400 nm

Genotoxicity of ultraviolet radiation with wavelength 300-400 nm (sunlight uVR) is mediated by the generation of reactive oxygen species. The research which was carried out on the base of developed early bacterial model indicated the existence of uV-protecting activity of allantoin, formed from uric acid in organisms of all vertebrates except human and anthropoid apes. The uric acid which is the end-product of purine catabolism in the organism of anthropoid apes, does not possess statistically significant protective effect. Safety of allanoin makes it a perspective component of sunlight protectors.

The genomes of the South American opossum ( Monodelphis domestica) and platypus ( Ornithorhynchus anatinus) encode a more complete purine catabolic pathway than placental mammals

The end product of purine catabolism varies amongst vertebrates and is a consequence of independent gene inactivation events that have truncated the purine catabolic pathway. Mammals have traditionally been grouped into two classes based on their end product of purine catabolism: most mammals, whose end product is allantoin due to an ancient loss of allantoinase (ALLN), and the hominoids, whose end product is uric acid due to recent inactivations of urate oxidase (UOX). However little is known about purine catabolism in marsupials and monotremes. Here we report the results of a comparative genomics study designed to characterize the purine catabolic pathway in a marsupial, the South American opossum ( Monodelphis domestica), and a monotreme, the platypus ( Ornithorhynchus anatinus). We found that both genomes encode a more complete set of genes for purine catabolism than do eutherians and conclude that a near complete purine catabolic pathway was present in the common ancestor of all mammals, and that the loss of ALLN is specific to placental mammals. Our results therefore provide a revised history for gene loss in the purine catabolic pathway and suggest that marsupials and monotremes represent a third class of mammals with respect to their end products of purine catabolism.

Mutations in the SLC2A9 Gene Cause Hyperuricosuria and Hyperuricemia in the Dog

Allantoin is the end product of purine catabolism in all mammals except humans, great apes, and one breed of dog, the Dalmatian. Humans and Dalmatian dogs produce uric acid during purine degradation, which leads to elevated levels of uric acid in blood and urine and can result in significant diseases in both species. The defect in Dalmatians results from inefficient transport of uric acid in both the liver and renal proximal tubules. Hyperuricosuria and hyperuricemia (huu) is a simple autosomal recessive trait for which all Dalmatian dogs are homozygous. Therefore, in order to map the locus, an interbreed backcross was used. Linkage mapping localized the huu trait to CFA03, which excluded the obvious urate transporter 1 gene, SLC22A12. Positional cloning placed the locus in a minimal interval of 2.5 Mb with a LOD score of 17.45. A critical interval of 333 kb containing only four genes was homozygous in all Dalmatians. Sequence and expression analyses of the SLC2A9 gene indicated three possible mutations, a missense mutation (G616T;C188F) and two promoter mutations that together appear to reduce the expression levels of one of the isoforms. The missense mutation is associated with hyperuricosuria in the Dalmatian, while the promoter SNPs occur in other unaffected breeds of dog. Verification of the causative nature of these changes was obtained when hyperuricosuric dogs from several other breeds were found to possess the same combination of mutations as found in the Dalmatian. The Dalmatian dog model of hyperuricosuria and hyperuricemia underscores the importance of SLC2A9 for uric acid transport in mammals.