Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.3.4.6 (urease)
 7,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bacillus fastidiosus was cultivated in batch and continuous culture on various carbon and nitrogen sources. The enzymes involved in allantoin degradation (allantoinase, urease, carboligase) of B. fastidiosus were hardly affected by either carbon or nitrogen source. In contrast, the enzymes involved in glycerol utilization (glycerol kinase, glycerol 3-phosphate dehydrogenase) were induced during growth on glycerol, but were not affected by the amount of allantoin present.
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PMID:The level of enzymes involved in the allantoin metabolism of Bacillus fastidiosus grown under different conditions. 776 82

A hydantoinase from Arthrobacter aurescens DSM 3745 has been purified to homogeneity with a yield of 77% using a three-step purification procedure. The active enzyme is a tetramer consisting of four identical subunits, each with a molecular mass of 49670 Da as determined by mass spectrometry. The N-terminal amino acid sequence of the enzyme indicates sequence identities to cyclic amidases involved in the nucleotide metabolism as the D-hydantoinase from Agrobacterium radiobacter (53%), the D-selective dihydropyrimidinase from Bacillus stearothermophilus (38%), the allantoinase from Rana catesbeiana (26%), as well as to the catalytic subunit of the urease from Helicobacter pylori (50%). However, all studies based on substrate-dependent growth, induction and catalytic behavior documented the novelty of the bacterial hydantoinase and that its physiological role is not related to any of these enzymes or known metabolic pathways. Its substrate specificity differs from hydantoinases listed in Enzyme Nomenclature and is rather more predominant for the cleavage of aryl- than for alkyl-hydantoin derivatives. It is shown that the stereoselectivity of this enzyme depends on the substrate used for bioconversion: although it is strictly L-selective for the cleavage of D,L-5-indolylmethylhydantoin, it appears to be D-selective for the hydrolysis of D,L-methylthioethylhydantoin. Due to these findings we conclude that this novel bacterial hydantoinase should be classified as a new member of the EC-group 3.5.2 of cyclic amidases.
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PMID:Substrate-dependent enantioselectivity of a novel hydantoinase from Arthrobacter aurescens DSM 3745: purification and characterization as new member of cyclic amidases. 965 Feb 83

Hydantoinases are valuable enzymes for the production of optically pure D- and L-amino acids. They catalyse the reversible hydrolytic ring cleavage of hydantoin or 5'-monosubstituted hydantoins and are therefore classified in the EC nomenclature as cyclic amidases (EC 3.5.2.). In the EC nomenclature, four different hydantoin-cleaving enzymes are described: dihydropyrimidinase (3.5.2.2), allantoinase (EC 3.5.2.5), carboxymethylhydantoinase (EC 3.5.2.4), and N-methylhydantoinase (EC 3.5.2.14). Beside these, other hydantoinases with known metabolic functions, such as imidase and carboxyethylhydantoinase and enzymes with unknown metabolic function, are described in the literature and have not yet been classified. An important question is whether the distinct hydantoinases, which are frequently classified as L-, D-, and non-selective hydantoinases depending on their substrate specificity and stereoselectivity, are related to each other. In order to investigate the evolutionary relationship, amino acid sequence data can be used for a phylogenetic analysis. Although most of these enzymes only share limited sequence homology (identity < 15%) and therefore are only distantly related, it can be shown (i) that most of them are members of a broad set of amidases with similarities to ureases and build a protein superfamily, whereas ATP-dependent hydantoinases are not related, (ii) that the urease-related amidases have evolved divergently from a common ancestor and (iii) that they share a metal-binding motif consisting of conserved histidine residues. The difference in enantioselectivity used for the classification of hydantoinases on the basis of their biotechnological value does not reflect their evolutionary relationship, which is to a more diverse group of enzymes than was assumed earlier. This protein superfamily probably has its origin in the prebiotic conditions of the primitive earth.
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PMID:Microbial hydantoinases--industrial enzymes from the origin of life? 1022 78

The degradation of xanthine was studied in young and aged leaves and in immature and mature fruits of Coffea arabica and Coffea dewevrei, which differ with respect to caffeine catabolism. Radioisotope feeding experiments showed that leaves degraded xanthine more readily than fruits but that mature fruits and aged leaves were less efficient than younger tissues. In all cases, a significant part of the recovered radioactivity was in the ureides. Xanthine dehydrogenase was characterized as the enzyme responsible for xanthine degradation, and its activity and that of uricase were consistent with the results obtained in the radioisotope feeding experiments. Activities of allantoinase and allantoate amidohydrolase could not be detected. Considerable levels of endogenous allantoin and allantoic acid were found in fruits and leaves. Therefore, ureide accumulation might be a consequence of low enzyme activity. There was no positive correlation between urease activity and the data from the radioisotope feeding experiments.
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PMID:Xanthine degradation and related enzyme activities in leaves and fruits of two coffea species differing in caffeine catabolism. 1055 61

Uric-acid-degrading enzymes (uricase, allantoinase, allantoicase, ureidoglycolate lyase and urease) were lost during vertebrate evolution and the causes for this loss are still unclear. We have recently cloned the first vertebrate allantoicase cDNA from the amphibian Xenopus laevis. Surprisingly, we have found some mammalian expressed sequence tags (ESTs) that show high similarity with Xenopus allantoicase cDNA. From a human fetal spleen cDNA library and adult kidney EST clone, we have obtained a 1790 nucleotide long cDNA. The 3' end of this sequence reveals a substantial high identity with the corresponding portion of Xenopus allantoicase cDNA. In contrast, at the 5' end the human sequence diverges from that of Xenopus; since no continuous open reading frame can be found in this region, the hypothetical human protein appears truncated at its N-terminus. We proposed that such a transcript could be due to an incorrect splicing mechanism that introduces an intron portion at the 5' end of human cDNA. Allantoicase cDNA is expressed in adult testis, prostate, kidney and fetal spleen. By comparison with available genomic sequences deposited in database, we have determined that the human allantoicase gene consists of five exons and spans 8kb. We have also mapped the gene in chromosome 2.
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PMID:Human allantoicase gene: cDNA cloning, genomic organization and chromosome localization. 1105 55

Allantoicase is one of the enzymes involved in uricolysis. The enzymes of this catabolic pathway (i.e. allantoinase, allantoicase, ureidoglycolate lyase and urease) were lost during vertebrate evolution and the causes for this loss are still unclear. In mammals, as well as in birds and reptiles, the activity of allantoicase is absent; notwithstanding, we recently cloned human and mouse cDNA sequences with high similarity with previously characterized allantoicases. In the present paper, we report the genomic organization of the allantoicase gene in mouse and in man. Both genes are constituted by 11 exons that appear to be very conserved; introns are more variable in length while maintain the same phase but for intron 4. We have also detected a second transcript of the human allantoicase gene in which exon 1 is absent. Moreover, the mouse gene maps in chromosome 12 at 13.0 cM from the centromere.
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PMID:Genomic organization and chromosome localization of the murine and human allantoicase gene. 1203 79

Agaricus bisporus is able to use urate, allantoin, allantoate, urea and alloxanate as nitrogen sources for growth. The presence of urate oxidase, allantoinase, ureidoglycolase and urease activities, both in fruit bodies and mycelia, points to a degradative pathway for urate similar to that found in various microorganisms. So far all efforts to demonstrate the enzyme responsible for allantoate degradation failed. A urease inhibitor appeared to be present in cell-free extracts from fruit bodies.
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PMID:Purine degradation in the edible mushroom Agaricus bisporus. 1263 Mar 18

Budgets for import and utilization of ureide, amides, and a range of amino acids were constructed for the developing first-formed fruit of symbiotically dependent cowpea (Vigna unguiculata [L.] Walp. cv Vita 3). Data on fruit total N economy, and analyses of the xylem and phloem streams serving the fruit, were used to predict the input of various solutes while the compositions of the soluble and protein pools of pod, seed coat, and embryo were used to estimate the net consumption of compounds. Ureides and amides provided virtually all of the fruit's N requirements for net synthesis of amino compounds supplied inadequately from the parent plant. Xylem was the principal source of ureide to the pod, while phloem was the major source of amides to pod and seed. All fruit parts showed in vitro activity of urease (EC 3.5.1.5), allantoinase (EC 3.5.2.5), asparaginase (EC 3.5.11), ammonia-assimilating enzymes and aspartate and alanine aminotransferases (EC 2.61.1 and EC 2.6.1.1.2). Asparagine:pyruvate aminotransferase (EC 2.6.1.14) was recovered only from the pod. The pod was initially the major site for processing and incorporating N; later seed coats and finally embryos became predominant. Ureides were broken down mainly in the pod and seed coat. Amide metabolism occurred in all fruit organs, but principally in the embryo during much of seed growth. Seed coats released N to embryos mainly as histidine, arginine, glutamine, and asparagine, hardly at all as ureide. Amino compounds delivered in noticeably deficient amounts to the fruit were arginine, histidine, glycine, glutamate, and aspartate, while seeds received insufficient arginine, histidine, serine, glycine, and alanine. Quantitatively based schemes are proposed depicting the principal metabolic transformation accompanying N-flow between seed compartments during development.
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PMID:Nitrogen nutrition and metabolic interconversions of nitrogenous solutes in developing cowpea fruits. 1666 63

Degradation of purines to uric acid is generally conserved among organisms, however, the end product of uric acid degradation varies from species to species depending on the presence of active catabolic enzymes. In humans, most higher primates and birds, the urate oxidase gene is non-functional and hence uric acid is not further broken down. Uric acid in human blood plasma serves as an antioxidant and an immune enhancer; conversely, excessive amounts cause the common affliction gout. In contrast, uric acid is completely degraded to ammonia in most fungi. Currently, relatively little is known about uric acid catabolism in the fungal pathogen Cryptococcus neoformans even though this yeast is commonly isolated from uric acid-rich pigeon guano. In addition, uric acid utilization enhances the production of the cryptococcal virulence factors capsule and urease, and may potentially modulate the host immune response during infection. Based on these important observations, we employed both Agrobacterium-mediated insertional mutagenesis and bioinformatics to predict all the uric acid catabolic enzyme-encoding genes in the H99 genome. The candidate C. neoformans uric acid catabolic genes identified were named: URO1 (urate oxidase), URO2 (HIU hydrolase), URO3 (OHCU decarboxylase), DAL1 (allantoinase), DAL2,3,3 (allantoicase-ureidoglycolate hydrolase fusion protein), and URE1 (urease). All six ORFs were then deleted via homologous recombination; assaying of the deletion mutants' ability to assimilate uric acid and its pathway intermediates as the sole nitrogen source validated their enzymatic functions. While Uro1, Uro2, Uro3, Dal1 and Dal2,3,3 were demonstrated to be dispensable for virulence, the significance of using a modified animal model system of cryptococcosis for improved mimicking of human pathogenicity is discussed.
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PMID:Characterization of the complete uric acid degradation pathway in the fungal pathogen Cryptococcus neoformans. 2366 4

Purines such as hypoxanthine, xanthine, uric acid, allantoin and allantoic acid serve as sole nitrogen sources for the yeast Schizosaccharomyces pombe. A number of classes of mutants unable to use purines have been isolated and genetically analysed. Mutants in the urol gene lack uricase, all1 lack allantoinase, ala1 lack allantoicase whilst in ure1, ure2, ure3 and ure4 genes lack urease activity. Mutants in four hyp genes are unable to convert hypoxanthine to uric acid whilst mutation in xan1 results in impaired growth with xanthine. hyp5 strains are unable to convert both hypoxanthine and xanthine to uric acid. The mutations are recessive and none of the loci are linked to each other. The possible catalytic steps involved are discussed.
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PMID:Genetic studies of purine breakdown in the fission yeast Schizosaccharomyces pombe. 2417 83


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