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)

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

Gyrocotyle fimbriata isolated from the spiral valve of Hydrolagus colliei were washed, then held in a filtered seawater-penicillin-Tris buffer medium. Ammonia and urea release to the medium declined together and ammonia production was minimal when the urea concentration was below detectable limits. Alanine and smaller amounts of glycine were released to the medium at a more constant rate. After 12 hr the alanine-glycine excretion was more than 20 times the ammonia excretion. L-arginine, L-serine, L-histidine, and urea were most effective in stimulating ammonia production by whole worms; other L-amino acids were essentially ineffective. L-glutamate dehydrogenase, L-amino acid oxidase, uricase, and ornithine transcarbamylase were below detectable levels. L-serine dehydrase, L-arginase, L-histidase, and urease were detected in tissue homogenates and probably account for most of the endogenous ammonia production. L-arginase has a molecular weight of 28,000 by Sehpadex gel filtration. The high levels of glutamate-pyruvate transaminase and lower levels of glutamate-oxalacetate transaminase correlate with the high level of alanine excretion. It is concluded that (1) ammonia production is not strongly linked to the overall energy metabolism of Gyrocotyle and is probably a result of a series of unrelated enzymatic reactions such as the action of urease of urea from the tissue of the rat fish, and (2) alanine and glycine are the major nitrogen excretory products and their production is linked to the energy metabolism of Gyrocotyle.
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PMID:Ammonia formation and amino acid excretion by Gyrocotyle fimbriata (Cestoidea). 111 78

A positive, genetic selection against the activity of the nitrogen regulatory (NTR) system was used to isolate insertion mutations affecting nitrogen regulation in Klebsiella aerogenes. Two classes of mutation were obtained: those affecting the NTR system itself and leading to the loss of almost all nitrogen regulation, and those affecting the nac locus and leading to a loss of nitrogen regulation of a family of nitrogen-regulated enzymes. The set of these nac-dependent enzymes included histidase, glutamate dehydrogenase, glutamate synthase, proline oxidase, and urease. The enzymes shown to be nac independent included glutamine synthetase, asparaginase, tryptophan permease, nitrate reductase, the product of the nifLA operon, and perhaps nitrite reductase. The expression of the nac gene was itself highly nitrogen regulated, and this regulation was mediated by the NTR system. The loss of nitrogen regulation was found in each of the four insertion mutants studied, showing that loss of nitrogen regulation resulted from the absence of nac function rather than from an altered form of the nac gene product. Thus we propose two classes of nitrogen-regulated operons: in class I, the NTR system directly activates expression of the operon; in class II, the NTR system activates nac expression and the product(s) of the nac locus activates expression of the operon.
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PMID:Role of the nac gene product in the nitrogen regulation of some NTR-regulated operons of Klebsiella aerogenes. 197 23

The levels of several enzymes involved in assimilation of different nitrogen compounds were investigated in Streptomyces clavuligerus in relation to the nitrogen source supplied to the cultures. Threonine dehydratase, serine dehydratase, proline dehydrogenase, histidase and urocanase were not decreased in the presence of ammonium. The latter two enzymes were induced by histidine in the culture medium, while proline dehydrogenase was induced by proline. Glutamine synthetase, urease and ornithine aminotransferase levels were higher with poor nitrogen sources and were repressed by ammonium. Arginase was induced by arginine and repressed by ammonium. Glutamine synthetase was rapidly inactivated upon addition of ammonium to the culture, and could be reactivated in vitro by treatment with snake venom phosphodiesterase, which suggested that adenylylation is involved in the inactivation. Three previously isolated mutants with abnormal glutamine synthetase activities showed pleiotropic effects on urease formation. All these data point to a mechanism controlling preferential utilization of some nitrogen sources in this species.
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PMID:Regulation of nitrogen catabolic enzymes in Streptomyces clavuligerus. 257 37

In Pseudomonas aeruginosa the formation of urease, histidase and some other enzymes involved in nitrogen assimilation is repressed by ammonia in the growth medium. The key metabolite in this process appears to be glutamine or a product derived from it, since ammonia and glutamate did not repress urease and histidase synthesis in a mutant lacking glutamine synthetase activity when growth was limited for glutamine. The synthesis of these enzymes was repressed in cells growing in the presence of excess glutamine. High levels of glutamine were also required for the derepression of NADP-dependent glutamate dehydrogenase formation in the glutamine synthetase-negative mutant.
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PMID:Nitrogen control in Pseudomonas aeruginosa: a role for glutamine in the regulations of the synthesis of nadp-dependent glutamate dehydrogenase, urease and histidase. 611 86

We have shown that the low histidase activity found in anaerobic, nitrogen-limited cultures of Klebsiella pneumoniae is due to repression of the right-hand hut operon. In addition, we have examined the effects of NO3- on the aerobic and anaerobic expression of catabolite- and NH4+-repressible enzymes in this organism. NO3- permitted anaerobic growth of K. pneumoniae in minimal medium containing histidine as the sole carbon source, and histidase and succinate dehydrogenase were derepressed during anaerobic growth in histidine/NO3- medium. Use of sucrose rather than histidine as the carbon source reversed the effects of NO3- and repressed histidase and succinate dehydrogenase activities. Anaerobic growth in sucrose/NO3- medium also uncoupled the expression of urease and glutamine synthetase.
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PMID:Effects of anaerobiosis and nitrate on the expression of succinate dehydrogenase and enzymes associated with nitrogen metabolism in Klebsiella pneumoniae. 612 18

In Klebsiella aerogenes, the formation of a large number of enzymes responds to the quality and quantity of the nitrogen source provided in the growth medium, and this regulation requires the action of the nitrogen regulatory (NTR) system in every case known. Nitrogen regulation of several operons requires not only the NTR system, but also NAC, the product of the nac gene, raising the question of whether the role of NAC is to activate operons directly or by modifying the specificity of the NTR system. We isolated an insertion of the transposon Tn5tac1 which puts nac gene expression under the control of the IPTG-inducible tac promoter rather than the nitrogen-responsive nac promoter. When IPTG was present, cells carrying the tac-nac fusion activated NAC-dependent operons and repressed NAC-repressible operons independent of the nitrogen supply and even in the absence of an active NTR system. Thus, NAC is sufficient to regulate operons like hut (encoding histidase) and gdh (encoding glutamate dehydrogenase), confirming the model that the NTR system activates nac expression and NAC activates hut and represses gdh. Activation of urease formation occurred at a lower level of NAC than that required for glutamate dehydrogenase repression, and activation of histidase formation required still more NAC.
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PMID:The product of the Klebsiella aerogenes nac (nitrogen assimilation control) gene is sufficient for activation of the hut operons and repression of the gdh operon. 845 54