Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

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.
...
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.
...
PMID:[Anabolic and catabolic enzymes of urea metabolism in a carbohydrate-utilizing strain of Candida guilliermondii]. 2 24

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.
...
PMID:Arginine catabolism in Aphanocapsa 6308. 10 70

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.
...
PMID:Nitrogen regulation of arginase in Neurospora crassa. 14 62

The authors prepared under experimental-industrial conditions paper indicator systems for the express identification of microbes, including carbohydrate discs (by the method of Nikitin et al.), and newly worked out types for the determination of the activity of cytochromoxidase, urease, indol formation, and indicator amino acid decarboxylases (lysin, ornithin, arginine). The use of paper indicator discs proved to be expedient for rationalization of laboratory diagnosis of bacterial intestinal infections.
...
PMID:[Stable paper indicator systems for rapid identification of microorganisms]. 21 61

Hydroxamic acids have been reported to be potent and specific inhibitors of urease (EC 3.5.1.5) activity of plant and bacterial origin. The present investigation was performed on the inhibitory effect of hydroxamic acid derivatives of naturally occurring amino acids on the urease activity of the Jack Bean and the alimentary tracts of rats. Methionine-hydroxamic acid was the most powerful inhibitor (I50=3.9 X 10(-6) M) among nineteen alpha-aminoacyl hydroxamic acids. Phenylalanine-, serine-, alanine-, glycine-, histidine-, threonine-, leucine-, and arginine-hydroxamic acids followed, in order of decreasing inhibitory power. The inhibition proceeded with time at a comparable rate to fatty acyl hydroxamic acid inhibition. The I50 values of alpha-aminoacyl hydroxamic acids were found to be almost equal to those of the corresponding fatty acyl hydroxamic acids. This fact shows that the alpha-amino group did not affect inhibitory power. However, aspartic-beta-, lysine-, and glutamic-gamma-hydroxamic acids, in descending order, were much less inhibitory, probably due to the presence of a carboxyl or omega-amino group. Furthermore, the pH optimum of the inhibition shifted to lower pH in the presence of a carboxyl group, and to a higher pH in e presence of an amino group. The results suggest that the dissociation of an acidic or a basic group reduces the inhibitory power of hydroxamic acid. Hydroxamic acid inhibits urease activity with strict specificity, excpet for aspartic-beta-hydroxamic acid, which inhibited asparaginase competitively. Hydroxamic acid derivatives of amino acids inhibited not only the urease activity of the Jack Bean, but also that of the caecum and ileum parts of the rat intestine.
...
PMID:Inhibition of urease activity by hydroxamic acid derivatives of amino acids. 23 68

The Oxi/Ferm test system was evaluated for accuracy and reliability for identification of nonfermentative and oxidase-positive fermentative bacteria by using 375 bacterial strains obtained from stock culture and clinical specimens. The Oxi/Ferm system is a compartmentalized tube containing eight media to provide nine biochemical test results. When combined with the oxidase test, the results corresponding to the positive reactions are totaled and the composite number is located in the coding manual to identify the organisms. The 375 isolates studied were evaluated for accuracy of identification, using both the original and revised code manuals. In comparison with the conventional media used, there was 100% correlation in tests for hydrogen sulfide and indole production, over 96% for nitrogen gas, arginine, and urease, over 92% for xylose and dextrose oxidation, and less than 90% for citrate utilization and dextrose fermentation. There was an overall accuracy in identification of 89.3% using the original manual, with accuracy revised slightly upward to 90.7% using the revised manual. There was 100% accuracy in identification with 44.0% of the strains tested (11 species) using the original manual and with 66.1% (16 species) using the revised manual. Thirteen of the 40 original misidentifications and 14 of 35 revised misidentifications resulted from failure to code and were unidentifiable by Oxi/Ferm. The remainder were incorrectly identified or could not be differentiated from closely related strains. Eleven strains of Alcaligenes odorans were correctly identified using the original code, whereas no code was provided in the revised manual. The Oxi/Ferm system is both simple and rapid and is satisfactory for identification of the more common isolates.
...
PMID:Evaluation of the oxi/ferm tube system with selected Gram-negative bacteria. 33 24

Uninduced cultures of Saccharomyces cerevisiae exhibit high basal levels of allantoinase, allantoicase, and ureidoglycolate hydrolase, the enzymes responsible for degrading allantoin to urea. As a result, these activities increase only 4- to 8-fold upon induction, whereas the urea-degrading enzymes, urea carboxylase and allophanate hydrolase, have very low basal levels and routinely increase 30-fold on induction. Differences in the inducibility of these five enzymes were somewhat surprising because they are all part of the same pathway and have the same inducer, allophanate. Our current studies reconcile these observations. S. cerevisiae normally contained up to 1 mM allantoin sequestered in a cellular organelle, most likely the vacuole. Separation of the large amounts of allantoin and the enzymes that degrade it provide the cell with an efficient nitrogen reserve. On starvation, sequestered allantoin likely becomes accessible to these degradative enzymes. Because they are already present at high levels, the fact that their inducer is considerably removed from the input allantoin is of little consequence. This suggests that at times metabolite compartmentation may play an equal role with enzyme induction in the regulation of allantoin metabolism. Metabolism of arginine, another sequestered metabolite, must be controlled both by induction of arginase and compartmentation because arginine serves both as a reserve nitrogen source and a precursor of protein synthesis. The latter function precludes the existence of high basal levels of arginase.
...
PMID:Metabolite compartmentation in Saccharomyces cerevisiae. 35 30

Twenty amino acids were examined for their effects on urinary orotic acid excretion. Except for arginine and ornithine, all of the remaining amino acids tested induced a mild orotic aciduria in rats 2 hours post feeding. Two ammonium salts, and urease also acted, as inducers of orotic aciduria. The ammoneogenic properties of the amino acids tested could not solely explain the induced excretion of orotic acid. Only serine, glutamine, NH4Cl, (NH4)2CO3, and urease increased orotic acid excretion in the 24 hour fasted rat. Administration of 0.5 mmoles of arginine or ornithine ameliorated the mild orotic aciduria induced by either glycine or lysine. Arginine was shown to be more efficacious in preventing glycine induced orotic aciduria than was ornithine. Amino acid induced orotic aciduria is dependent upon the physiological state of the animal, varying with the state of digestion and the supply of arginine.
...
PMID:Amino acid induced orotic aciduria. 63 45

Larvae of the bruchid beetle Caryedes brasiliensis feed exclusively on seeds of the Neotropical legume Dioclea megacarpa, which contains 13 percent L-canavanine by dry weight. L-Canavanine, a nonprotein amino acid analog of L-arginine, exhibits potent insecticidal properties. Most of the seed nitrogen is sequestered in canavanine, and bruchid beetle larvae do not simply excrete this toxic compound. Instead, these larvae possess extraordinarily high urease activity, which facilitates the conversion of canavanine to ammonia through urea. In this way, canavanine is effectively detoxified and a supply of nitrogen for fixation into organic linkage is ensured.
...
PMID:Degradation and detoxification of canavanine by a specialized seed predator. 85 40


1 2 3 4 5 6 7 8 9 10 Next >>

---