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)

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

The NAC (nitrogen assimilation control) protein from Klebsiella aerogenes is a LysR-like regulator for transcription of several operons involved in nitrogen metabolism, and couples the transcription of these sigma 70-dependent operons to regulation by the sigma 54-dependent NTR system. NAC activates expression of operons (e.g. histidine utilization, hut), allowing use of poor nitrogen sources, and represses expression of operons (e.g. glutamate dehydrogenase, gdh) allowing assimilation of the preferred nitrogen source, ammonium. NAC is both necessary and sufficient to activate transcription, but the expression of the nac gene is totally dependent on the central nitrogen regulatory system (NTR) and RNA polymerase carrying the sigma 54 sigma factor (RNAP sigma 54). Nitrogen starvation signals the NTR system to transcribe nac, and NAC activates the transcription of hut, put (proline utilization), and urease. NAC does not affect the transcription of RNAP sigma 54-dependent operons like ginA or nifLA, which respond directly to the NTR system, but activates transcription of RNAP sigma 70-dependent operons. Thus NAC acts as a bridge between RNAP sigma 70-dependent operons like hut and the RNAP sigma 54-dependent NTR system. The activation of operons like hut by NAC in response to nitrogen starvation is at least superficially similar to their activation by CAP-cAMP in response to carbon and energy starvation.
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PMID:The role of the NAC protein in the nitrogen regulation of Klebsiella aerogenes. 166 20

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

We present a study of the enzymatic activities involved in the pathway for arginine catabolism by Agrobacterium tumefaciens. Nitrogen from arginine is recovered through the arginase-urease pathway; the genes for these two activities are probably chromosomally born. Arginase was found to be inducible during growth in the presence of arginine or ornithine. Urease was constitutively expressed. Ornithine, resulting from the action of arginase on arginine, could be used as a nitrogen source via transamination to delta 1-pyrroline-5-carboxylate and reduction of the latter compound to proline by a reductase (both enzymatic activities are probably chromosomally encoded). Ornithine could also be used as a carbon source. Thus, we identified an ornithine cyclase activity that was responsible for direct conversion of ornithine to proline. This activity was found to be Ti plasmid encoded and inducible by growth in medium containing octopine or nopaline. The same activity was also chromosomally encoded in some Agrobacterium strains. In such strains, this activity was inducible during growth in arginine-containing medium.
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PMID:Arginine catabolism in Agrobacterium strains: role of the Ti plasmid. 395 72

L-usnic acid inactivates urease through a process which implicates the blockade of--SH groups in parallel to the formation of inactive polymers. Both L-alanine and L-proline partially reverses the inactivation and effectively diminishes the amount of highly polymerized protein. The amino acids also prevent the linkage of L-usnic acid on the sites of low affinity for the ligand, being then related to the sites of polymerization.
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PMID:L-usnate-urease interactions: binding sites for polymerization. 622 56

Urea production by cortical (CCD) and medullary (OMCD) collecting ducts of the rat kidney was measured in vitro by incubating single microdissected pieces of tubule in the presence of L-[guanido-14C]arginine (0.2 mM). The [14C]urea released from the cells was hydrolysed in presence of urease added to the incubation medium and the 14CO2 formed was trapped in KOH and counted. The effect of various amino acids (AA) on urea production was investigated by adding unlabelled AA (either in combination or singly) at concentrations close to those present in blood plasma. A mixture of 17 AA decreased urea production from [14C]arginine by 46% in CCD and by 58% in OMCD. When lysine and proline were omitted from the mixture, the inhibition was less marked (19% in CCD and 43% in OMCD, respectively). When AA were tested singly, lysine induced the larger inhibition (40% in CCD and 45% in OMCD), than ornithine and glutamine (about 15% each, in CCD and OMCD), whereas proline inhibition (7% in CCD, 10% in OMCD) was not statistically significant. Branched-chain amino acids (BCAA) in combination (leucine, isoleucine and valine) also markedly reduced urea production by CCD and OMCD. Their effect was dose dependent. Solubilization of CCD and OMCD cell membranes with Triton X-100 resulted in a twofold increase in urea production by control samples; the relative inhibition (per cent) induced by BCAA was enhanced, whereas that induced by lysine was decreased. The data suggest that, in living tubules, the inhibition obtained with lysine resulted, for a large part, from competition between lysine and arginine for cell uptake via a common membrane carrier, whereas the inhibition induced by BCAA corresponded to an effect on arginase activity itself.
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PMID:Urea production by kidney collecting ducts in vitro: effect of amino acid addition. 805 17

Incubation of mixed human saliva with arginine, ornithine, and proline for 30 min to 2 h at 40 degrees C leads to an appreciable consumption of the above amino acids. The rate of utilization is 0.2 to 0.5 ncat/ml of saliva. The rate of urea loss is higher by an order of magnitude: up to 11 ncat/ml. Putrescin, urea (after incubation with arginine), and ammonium are identified as the products of these reactions. The biological significance of such reactions is believed to consist in neutralization of carbohydrate fermentation products. The detected consumption of amino acids and urea indicates that mixed human saliva contains urease, arginase, ornithine decarboxylase, and, probably, proline reductase. Since the origin of these enzymes is probably bacterial, changes in their activity in the saliva can be regarded as an indicator of dysbacteriosis and a diagnostically important parameter.
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PMID:[The utilization of amino acids and urea by human oral fluid]. 947 2

Investigations of faeces samples from breeding stocks of companion birds in the federal state of Thuringia revealed a high contamination rate of companion birds with Cryptococcus (Cr.) neoformans var. neoformans. The prevalence of Cr. neoformans var. neoformans correlated with the spectrum of bird species present in the respective breeding units. The causes for that are not clear at the moment. Sensitivity of Cr. neoformans var. neoformans towards alkaline agents was not confirmed and was ruled out as a reason for different tenacity of the yeast in various bird breedings. Differentiation of varieties within Cr. neoformans was possible on the basis of proline assimilation, determination of canavanine resistance, EDTA urease test, as well as Cr. neoformans var. neoformans factor sera and PCR fingerprinting. Serological differentiation of serovars and PCR fingerprinting resulted in subdivision of Cr. neoformans var. neoformans isolates into two groups, which corresponded to serovars A and D. A prevalence of serovar A isolates was found in investigated bird breeding stocks. This also corresponded to the distribution of Cr. neoformans var. neoformans described in literature in humans with cryptococcosis in Germany. Consequently, serovar A or D infections of patients may be connected with their contacts to Cr. neoformans-excreting companion birds.
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PMID:[Distribution, serovar affiliation and epidemiologic behavior of Cryptococcus neoformans isolates from ornamental bird breeds]. 979 37

The Cryptococcus neoformans strains isolated from two human cases could be diagnosed as Cr. neoformans var. neoformans by differentiation on the basis of their characteristics determined by proline, canavanine and EDTA urease tests. The results of the serovar assignment were: for the isolate from the meningoencephalitis patient with lethal outcome, serovar A; for the strain isolated from the osteomyelitis patient with benign course, serovar D. Also, the PCR fingerprinting using primers (GACA)4, (CAC)5 and FM 1 resulted in a clear and reproducible assignment of the Cr. neoformans strains to the varieties neoformans and gattii, respectively, and, in addition, it confirmed the serovar assignment. No statistically confirmed differences in virulence between the osteomyelitis and the meningoencephalitis strain could be established by i.v. testing in mice, nor did the PCR with several primers provide any clues to a genetically determined higher virulence of the meningoencephalitis strain. The different classification as serovars A and D does not allow any conclusions concerning different virulence. It was not possible to retrospectively establish the sources of infection of the two Cr. neoformans infections, but pigeon faeces may well have played a role as a reservoir for one of the illnesses.
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PMID:Phenotypic and genotypic differentiation of several human and avian isolates of Cryptococcus neoformans. 991 62

A pot experiment with rice under submerged condition showed that with the increase of Cd concentration, soil microbial biomass carbon (Cmic) and nitrogen (Nmic) increased initially but decreased at a certain concentration, and the turning points varied with different soil types. Soil enzyme activities had the similar variation trend with soil Cmic and Nmic, and the turning points varied with different soil types and soil enzymes. The variation coefficients were in order of dehydrogenase activity > acid phophatase activity > urease activity. Soil respiration rate and metabolic quotient increased tardily with increasing cadmium concentration. The chlorophyll content of rice increased initially but decreased then with the increase of Cd contamination, and the turning points differed with different soil types. Rice proline content and peroxidase activity were enhanced gradually with increasing cadmium concentration. The variation coefficients of rice physiological indices on paddy soils derived from silty loam and clayed red earth were in order of peroxidase activity > chlorophyll content > proline content, and peroxidase activity > proline content > chlorophyll content, respectively. Correlation analysis indicated that there was a close correlation between the variations of soil microbial biomass and enzymatic activities and rice physiological indices under Cd contamination.
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PMID:[Effects of Cd contamination on paddy soil microbial biomass and enzyme activities and rice physiological indices]. 1647 60


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