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

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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)

Growing steers were used in a replicated 3 X 3 Latin square to study the influence of ionophores on mineral metabolism and ruminal urease activity. Treatments consisted of: 1) basal high energy diet; 2) basal plus 33 ppm lasalocid and 3) basal plus 33 ppm monensin. Each period was 33 days and apparent absorption and retention of macrominerals were measured during the last 5 days of each period. Mineral intake during the collection period was not affected by treatment. Both ionophores increased apparent absorption of sodium, magnesium and phosphorus. Retention of magnesium and phosphorus were higher for steers receiving either lasalocid or monensin. Potassium and calcium absorption were not significantly affected by treatment. Serum concentrations of macrominerals were similar for all treatments. Zinc and copper concentrations in serum were higher in animals fed monensin or lasalocid. Steers fed either ionophore had lower concentrations of soluble potassium and calcium in rumen fluid. Both ionophores also decreased ruminal osmolality. Bacterial urease, a nickel-dependent enzyme, was decreased by 28 and 66% in animals that received lasalocid and monensin, respectively. These findings indicate that lasalocid and monensin affect metabolism of certain minerals in ruminants.
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PMID:Influence of monensin and lasalocid on mineral metabolism and ruminal urease activity in steers. 669 34

Day-old pigs were individually fed a low nickel (0.16 ppm) liquid milk-based diet supplemented with either 0, 5 or 25 ppm nickel on a dry matter basis for a 21-day period. At the end of the liquid feeding period, five pigs per treatment were killed, and the remaining five were fed a dried skim milk-based diet (0.12 ppm nickel) with similar levels of added nickel for an additional 28 days. Dietary nickel did not affect animal gain, liver cholesterol, serum protein concentrations or bacterial urease activity in the gastrointestinal tract. The addition of 5 ppm nickel to the basal dry diet reduced ammonia concentrations in the cecum by 33%. Pigs receiving the high level of nickel had decreased serum alkaline phosphatase and increased serum glucose at 49 days, compared to controls. Animals receiving 5 ppm nickel had higher liver iron and zinc concentrations than controls at 21 days but not at 49 days. Control pigs had lower kidney and lung nickel concentrations than animals receiving 5 ppm nickel at 21 days but not at 49 days. Increasing dietary nickel from 5 to 25 ppm resulted in increased concentrations of nickel in serum, kidney, lung, spleen and muscle. These results suggest that 0.12-0.16 ppm nickel is adequate for growth of neonatal pigs fed milk-based diets. However, additional nickel may improve the iron and zinc status of the young pig.
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PMID:Effect of dietary nickel on growth, urease activity, blood parameters and tissue mineral concentrations in the neonatal pig. 672 54

Preliminary results of an extended X-ray absorption fine structure (e.x.a.f.s.) and X-ray absorption near edge structure study of jack bean urease have recently been reported [Hasnain & Piggott (1983) Biochem. Biophys. Res. Commun. 112, 279]. These results indicate that the environment of the nickel ion in the enzyme is similar to that in the model compounds Ni(L)2(L')1(ClO4)1 (where L is 1-n-propyl-2-alpha-hydroxybenzylbenzimidazole and L' is the deprotonated form) and Ni(HMB)3(Br)2 (where HMB is 2-hydroxymethylbenzimidazole), the closest similarity being with Ni(L)2-(L')1(ClO4)1. A detailed e.x.a.f.s. analysis has now been carried out and the crystal structures of the two model compounds solved. These results are reported here.
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PMID:The nickel ion environment in jack bean urease. 674 89

Aspergillus nidulans can utilize urea as a sole source of nitrogen but not as a carbon source. Urea is degraded by a urease. Mutation at any one of three genes, ureB, ureC, and ureD, may result in deficient urease activity. The ureB gene is closely linked to ureA, the structural gene for the urea transport protein. The heat lability of ureB- revertant strain, intragenic complementation tests, and the linkage of ureB to ureA suggest that ureB is the urease structural gene. The ureD gene is probably involved in the synthesis or incorporation of a nickel cofactor essential for urease activity. The function of the ureC gene is not known. Urease is not induced but is subject to nitrogen regulation. The urease activities of ammonium-derepressed mutants show that the effector of nitrogen regulation is more likely to be glutamine than ammonium. When glutamine is present in the medium, urease appears to be inactivated by some means which does not involve a newly synthesized protease or a direct interaction between glutamine and urease.
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PMID:The regulation of urease activity in Aspergillus nidulans. 675 31

Acetamide and N-methylurea have been shown for the first time to be substrates for jack bean urease. In the enzymatic hydrolysis of urea, formamide, acetamide, and N-methylurea at pH 7.0 and 38 degrees C, kcat has the values 5870, 85, 0.55, and 0.075 s-1, respectively. The urease-catalyzed hydrolysis of all these substrates involves the active-site nickel ion(s). Enzymatic hydrolysis of the following compounds could not be detected: phenyl formate, p-nitroformanilide, trifluoroacetamide, p-nitrophenyl carbamate, thiourea, and O-methylisouronium ion. In the enzymatic hydrolysis of urea, the pH dependence of kcat between pH 3.4 and 7.8 indicates that at least two prototropic forms are active. Enzymatic hydrolysis of urea in the presence of methanol gave no detectable methyl carbamate. A mechanism of action for urease is proposed which involves initially an O-bonded complex between urea and an active-site Ni2+ ion and subsequently an O-bonded carbamato-enzyme intermediate.
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PMID:Jack bean urease (EC 3.5.1.5). V. On the mechanism of action of urease on urea, formamide, acetamide, N-methylurea, and related compounds. 678 53

At low pH, EDTA promotes the loss of the tightly bound nickel ions from jack bean urease. The specific activity of soluble enzyme after partial EDTA-promoted inactivation is a linear function of the nickel content. The results are consistent with the presence of 2.0 nickel ions per 97 000-dalton subunit in pure urease. The time scale for loss of enzymatic activity and nickel under these conditions is similar to that for loss of the "abnormal" tail absorption in the ultraviolet and visible absorption spectrum of urease (including the shoulder at approximately 420 nm). This indicates that nickel in urease is essential for enzymatic activity and establishes that the metal ions are in part responsible for the tail absorption in the ultraviolet spectrum of urease. After partial inactivation in the presence of EDTA either at low pH or in 2.5 M guanidinium chloride at neutral pH, urease did not regain activity in the presence of Ni2+. As yet apourease has not been produced reversibly. Jack bean seeds grown hydroponically without added nickel were low in both urease activity and nickel (10 and 6%, respectively, of parent seeds). Several other metal ions were readily available. This result suggests that metal ions other than nickel cannot substitute for nickel in the formation of normally active urease.
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PMID:Jack been urease (EC 3.5.1.5). II. The relationship between nickel, enzymatic activity, and the "abnormal" ultraviolet spectrum. The nickel content of jack beans. 679 94

EXAFS and XANES spectra have been recorded above the nickel K edge of urease and three model compounds. Preliminary results indicate that the local environment of the nickel ions in urease resemble most closely that of the nickel ions in the model compound [Ni(L)2(L*)1] (ClO4)1, where L is 1-n-propyl-2-alpha-hydroxybenzyl benzimidazole and L* is the deprotonated form.
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PMID:An EXAFS study of jack bean urease, a nickel metalloenzyme. 683 12

The addition of nickel ions restored urease activity in vivo and ability to grow on urea in a mutant strain of Aspergillus nidulans otherwise unable to utilize urea. This train carries a mutation in the ureD locus, one of four loci involved in urea utilization. No other urease-deficient strains tested responded to the presence of nickel ions. The analogous characteristics of the ureD mutant and the nitrate reductase and xanthine dehydrogenase associated cnxE mutants in Aspergillus nidulans are discussed. It is postulated that the ureD locus is in some way involved in the production or incorporation of a nickel cofactor essential for urease activity.
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PMID:Nickel requirement of a urease-deficient mutant in Aspergillus nidulans. 698 44

Kinetic, spectral, and other studies establish that hydroxamic acids bind reversibly to active-site nickel ion in jack bean urease. Equilibrium ultracentrifugation studies establish that the molecular weight of native urease is 590 000 +/- 30 000 while that of the subunit formed in 6 M guanidinium chloride in the presence of beta-mercaptoethanol is approximately 95 000. Essentially the same subunit molecular weight (approximately 93 000) is found by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, subsequent to denaturation in a guanidinium chloride - beta-mercaptoethanol system at various temperatures. Coupled with an equivalent weight of 96 600 for binding of the inhibitors acetohydroxamic acid and phosphoramidate, these results establish securely that urease is a hexamer with one active site per 96 600-dalton subunit. Consistent values for the equivalent weight are obtained by a routine spectrophotometric titration of the active site of freshly prepared urease with trans-cinnamoylhydroxamic acid. General equations are derived which describe spectrophotometric titrations of binding sites of any enzyme with a reversible inhibitor. These equations allow the evaluation of the difference spectrum of the protein-inhibitor complex even when the binding sites cannot readily be saturated with the inhibitor or vice versa.
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PMID:Jack bean urease (EC 3.5.1.5). IV. The molecular size and the mechanism of inhibition by hydroxamic acids. Spectrophotometric titration of enzymes with reversible inhibitors. 724 34

A simple and inexpensive procedure for determination of microgram quantities of metal ions in proteins is described and tested with nickel and iron. The method involves (a) dry ashing in an oxygen atmosphere at 450-460 degrees C in Pyrex vessels, (b) conversion of the metal oxides or other compounds to readily soluble species, and (c) spectrophotometric analysis. An improved procedure for the direct spectrophotometric determination of nickel using dimethylglyoxime is accurate to +/- 2% or better with samples of 1-5 microgram of nickel. These techniques were used to determine that the nickel content of freshly prepared jack bean urease in 2.00 +/- 0.12 g-at./96 600 g protein. The corresponds to 2.0 nickel ions per subunit. This result was confirmed by atomic absorption analysis, which also showed that calcium, manganese, cobalt, and iron are not present in significant amounts in urease.
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PMID:Jack bean urease (EC 3.5.1.5). I. A simple dry ashing procedure for the microdetermination of trace metals in proteins. The nickel content of urease. 727 35


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