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)

Urease was purified 24-fold from extracts of Klebsiella aerogenes. The enzyme has a molecular weight of 230,000 as determined by gel filtration, is highly substrate specific, and has a Km for urea of 0.7 mM. A mutant strain lacking urease was isolated; it failed to grow with urea as the sole source of nitrogen but did grow on media containing other nitrogen sources such as ammonia, histidine, or arginine. Urease was present at a high level when the cells were starved for nitrogen; its synthesis was repressed when the external ammonia concentration was high. Formation of urease did not require induction by urea and was not subject to catabolite repression. Its synthesis was controlled by glutamine synthetase. Mutants lacking glutamine synthetase failed to produce urease, and mutants forming glutamine synthetase at a high constitutive level also formed urease constitutively. Thus, the formation of urease is regulated like that of other enzymes of K. aerogenes capable of supplying the cell with ammonia or glutamate.
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PMID:Urease of Klebsiella aerogenes: control of its synthesis by glutamine synthetase. 1 38

The yeast "H" of the genus Candida guilliermondii can grow on hydrocarbons as the only source for carbon. Urea can serve as a nitrogen source for this yeast which lacks detectable urease activity. During urea metabolism ammonia has never been accumulated in the culture medium. However, transferring the yeast from complete urea-medium into an urea containing phophate-buffer, the degradation of urea continues and ammonia is accumulated as well as CO2 evolved. In cell-free extracts of the yeast urea amidolyase activity was detected in the presence of ATP, biotin and specific cations. Obviously, the synthesis of urea amidolyase is induced by urea and arginine and repressed by the catabolite ammonia. Similarly the synthesis of arginase is regulated by arginine and ammonia. The analytical data of the arginase action differ significantly in relation to the carbon source of the culture medium. Both the level of arginase and ornithine carbamyl-transferase change in a characteristic way during the batch-culture. From the lower level of arginase in relation to ornithine carbamyltransferase it can be concluded that especially in alkane-metabolizing yeast the arginine catabolism is not very intensive.
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PMID:[Anabolic and catabolic enzymes of urea metabolism in a carbohydrate-utilizing strain of Candida guilliermondii]. 2 24

We have partially characterized the biochemical parameters of glutamine synthetase from Klebsiella pneumoniae and have shown that the differential affinity of adenylylated and unadenylylated glutamine synthetase for adenosine diphosphate provides a convenient means of determining the adenylylation state. Using this assay procedure, we examined the relationship between the adenylylation state and the expression of other genes involved in nitrogen assimilation. We observed no correlation between the adenylylation state and the expression of histidase, glutamine synthetase, glutamate synthase, glutamate dehydrogenase, and urease in aerobic cultures.
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PMID:Relation between the adenylylation state of glutamine synthetase and the expression of other genes involved in nitrogen metabolism. 3 15

Mutants of Apergillus nidulans with lesions in a gene, areA (formerly called amdT), have been isolated by a variety of different selection methods. The areA mutants show a range of pleiotropic growth responses to a number of compounds as sole nitrogen sources, but are normal in utilization of carbon sources. The levels of two amidase enzymes as well as urease have been investigated in the mutants and have been shown to be affected by this gene. Most of the areA mutants have much lower amidase-specific activities when grown in ammonium-containing medium, compared with mycelium incubated in medium lacking a nitrogen source. Some of the areA mutants do not show derepression of urease upon relief of ammonium repression. The dominance relationships of areA alleles have been investigated in heterozygous diploids, and these studies lend support to the proposal that areA codes for a positively acting regulatory product. One of the new areA alleles is partially dominant to areA+ and areA102. This may be a result of negative complementation or indicate that areA has an additional negative regulatory function. Investigation of various amdR; areA double mutants has led to the conclusion that amdR and areA participate in independent regulatory circuits in the control of acetamide utilization. Studies on an amdRc; areA double mutant indicate that areA is involved in derepression of acetamidase upon relief of ammonium repression.
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PMID:Studies on the role of the areA gene in the regulation of nitrogen catabolism in Aspergillus nidulans. 5 52

The growth and utilization of nitrogen by intensive Chlorella vulgaris in wastes from production of urea, containing 1300 mg NH4+-N and 4000 mg urea-N/1, was investigated. In these conditions only Chlorella vulgaris AA strain, adapted to high concentrations of ammonia nitrogen, was able to grow. The elimination of nitrogen by continuous cultures was 750 mg urea-N/1 with 5-day flow rate. A considerable part of the urea was hydrolized by urease bacteria and removed in the form of NH3. The effect of intermittent light on the growth of algae was also studied. The better growth than in continuous light, was obtained with alternate one hour periods of light and darkness. Good results were also obtained with the use of 12 hour light and 12 hour darkness.
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PMID:Studies on the purification of wastes from the nitrogen fertilizer industry by intensive algal cultures. IV. growth of Chlorella vulgaris in wastes with high nitrogen content in continuous and intermittent light. 6 57

The catabolic products of arginine metabolism were observed in Aphanocapsa 6308, a unicellular cyanobacterium, by thin layer chromatography of growth media, by limiting growth conditions, and by enzymatic analysis. Of the organic, nitrogenous compounds examined, only arginine supported growth in CO2-free media. The excretion of ornithine at a concentration level greater than citrulline suggested the existence in Aphanocapsa 6308 of the arginine dihydrolase pathway which produced ornithine, CO2,NH4,+ adenosine 5'-triphosphate. Its existence was confirmed by enzymatic analysis. Although cells could not grow on urea as a sole carbon source a very active urease and subsequently an arginase were also demonstrated, indicating that Aphanocapsa can metabolize arginine via the arginase pathway. The level of enzymes for both pathways indicates a lack of genetic control. It is suggested that the arginase pathway provides only nitrogen for the cells wheras the arginine dihydrolase pathway provides not only nitrogen, but also CO2 and adenosine 5'-triphosphate.
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PMID:Arginine catabolism in Aphanocapsa 6308. 10 70

Strains of purple sulfur bacteria (Chromatium minutissimum, Ectothiorhodospira shaposhnikovii, Thiocapsa roseopersicina, Lamprobacter modestohalophilus) and nonsulfur bacteria (Rhodopseudomonas palustris, Rh. spheroides, Rhodospirillum rubrum) grow in media containing urea as a source of nitrogen at concentrations from 0.5 to 5.0%. They can also utilize the carbon of urea and thus grow in the absence of bicarbonate. Urea is decomposed by all the studied purple bacteria with the participation of urease. In a number of strains, the enzyme is inducible and is synthesized only in the presence of urea. However, it is constitutive in certain purple bacteria (L. modestohalophilus, Rh. palustris, Rh. spheroides). The strains of purple bacteria differ in the activity of urease and in its susceptibility to ammonium ions.
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PMID:[Use of urea by purple bacteria]. 11 59

The final products of the arginine catabolism that can be utilized as a nitrogen source in Neurospora crassa are ammonium, glutamic acid, and glutamine. The effect of these compounds on arginase induction by arginine was studied. In wild-type strain 74-A, induction by arginine was almost completely repressed by glutamic acid plus ammonium, whereas ammonium or glutamic acid alone had only moderate effects. Arginine products of catabolism also repressed arginase induction. A mutant, ure-1, which lacks urease activity, hyperinduced its arginase with arginine as a nitrogen source. The addition of either ammonium or glutamine produced effects similar to those in the wild-type strain. The effect of ammonium on arginase induction is mediated through its conversion into glutamine. This was demonstrated in mutant am-1, which lacks L-glutamate dehydrogenase activity. In this mutant, the effect of glutamic acid was reduced, and, with ammonium, it was completely lost. The addition of glutamine or glutamic acid plus ammonium to this strain decreased by threefold the induction of arginase by arginine. Proline, a final product of arginine catabolism, competitively inhibited arginase activity. This effect and the repression of arginase by glutamine are examples of negative modulation of the first enzyme in a catabolic pathway by its final products.
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PMID:Nitrogen regulation of arginase in Neurospora crassa. 14 62

Urease activity, expressed as mg N-NH3/g dry weight per 30 min at 25 degrees C, was determined in the various parts of the sheep, chicken and pig digestive apparatus. The results were as follows. Sheep: contents--rumen 1.25"/-0.09, reticulum 0.78+/-0.02, omasum 0.44+/-0.02, abomasum 0.002+/-0.001, duodenum 0.003+/-0.001, jejunum 0.18+/-0.03, ileum 0.42+/-0.03, caecum 1.34+/-0.11, colon 0.76+/-0.08, walls-rumen 0.88+/-0.16, reticulum 0.38+/-0.04, omasum 0.11+/-0.02, abomasum 0.01+/-0.002, ileum 0.092+/-0.01, caecum 0.14+/-0.03, colon 0.16+/-0.02. Chicken: contents--jejunum 0.028+/-0.009, ileum 0.043+/-0.013, caecum 0.17+/-0.03, colon and cloaca 0.04+/-0.013. Pigs: contents--jejunum 0.02+/-0.01, ileum 0.14+/-0.08, caecum 0.62+-0.12, colon 0.43+/-0.06. No urease activity was found in the walls of the digestive apparatus or the contents of the duodenum in chickens, or in the walls of the stomach and intestine and the contents of the duodenum in pigs. The results show that urease activity in the digestive apparatus of pigs and poultry is lower than in sheep. Inadequate urease activity in the digestive apparatus explains why chickens and pigs are significantly less capable than ruminants of utilizing urea nitrogen as a substitute for some of the protein in the diet.
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PMID:Urease activity in the contents and tissues of the sheep, pig and chicken gastrointestinal apparatus. 16 May 76

A simplified, concise scheme was developed for the identification of nonfermentative, gram-negative bacteria which have most frequently been reported in the literature as definite or possible agents of human disease. These organisms included apyocyanogenic Pseudomonas aeruginosa, P. fluorescens, P. putida, P. stutzeri, P. maltophilia, P. putrefaciens, P. cepacia, P. alcaligenes, FLAVOBACTERIUM SPECIES, Bordetella bronchiseptica, Acinetobacter anitratum (Herellea vaginicola), A. Iwoffi (Mima polymorpha), Moraxella species, Alcaligenes odorans and Alcaligenes species. The tests used for identification included production of cytochrome oxidase, amylase, deoxyribonuclease, gelatinase, urease and Beta-galactosidase; motility; oxidation of one per cent glucose and ten per cent lactose; fluorescence; indole, hydrogen sulfide and nitrogen gas production; denitrification of nitrites; growth at 42C; penicillin sensitivity and production of an aromatic odor and greenish discoloration on blood agar. Using this scheme, 85 per cent of 243 isolates (unknowns and reference strains) were identified to genus and species. Of the 15 per cent remaining, 11 per cent were identified as alkaline organisms and four per cent were unidentifiable.
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PMID:Identification of nonfermentative gram-negative bacteria in the clinical laboratory. 16 60


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