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 tetranuclear aggregate (enH(2))[Fe(4)(mu(3)-O)(heidi)(4)(mu-O,O'-O(2)CNHC(2)H(4)NH(3))] x 4H(2)O contains a novel bidentate zwitterionic carbamic acid ligand. Magnetic studies indicate that the unsymmetrical Fe(4) core is ferrimagnetic with an S=4 ground state. Similar ligands have been obtained on rectangular tetranuclear aggregates [M(4)(mu-O)(mu-OH)(hpdta)(2)(mu-X)(2)](n-) (M[double bond]Fe, Al, Ga). The carbamic acid ligands are considered to result from the hydrolytic activation (fixation) of atmospheric CO(2) by the aggregate precursor to give a carbonato intermediate, which then reacts with the organic diamine used as base in the synthesis. Similar aggregates with acetate ligands result from hydrolytic activation of the DMA used as cosolvent. Closely related mechanisms for these two activation processes are proposed, which are also related to the accepted mechanisms for carbonic anhydrase and urease.
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PMID:Biomimetic hydrolytic activation by Fe(III) aggregates: structures, reactivity and properties of novel oxo-bridged iron complexes. 1212 74

At the active site of urease, urea undergoes nucleophilic attack by water, whereas urea decomposes in solution by elimination of ammonia so that its rate of spontaneous hydrolysis is unknown. Quantum mechanical simulations have been interpreted as indicating that urea hydrolysis is extremely slow, compared with other biological reactions proceeding spontaneously, and that urease surpasses all other enzymes in its power to enhance the rate of a reaction. We tested that possibility experimentally by examining the hydrolysis of 1,1,3,3-tetramethylurea, from which elimination cannot occur. In neutral solution at 25 degrees C, the rate constant for the uncatalyzed hydrolysis of tetramethylurea is 4.2 x 10-12 s-1, which does not differ greatly from the rate constants observed for the uncatalyzed hydrolysis of acetamide (5.1 x 10-11 s-1) or N,N-dimethylacetamide (1.8 x 10-11 s-1) under the same conditions. We estimate that the proficiency of urease as a catalyst, (kcat/Km)/knon, is 8 x 1017 M-1, slightly higher than the values for other metalloenzymes (carboxypeptidase b and cytidine deaminase) that catalyze the hydrolysis of similar bonds.
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PMID:The burden borne by urease. 1607 78

A bacterium that converted daidzein to O-desmethylangolensin was isolated from the feces of healthy humans. It was an obligately anaerobic, nonsporeforming, nonmotile and Gram-positive rod. The isolate used glucose, sucrose, raffinose, maltose, and fructose as carbon sources. It did not hydrolyze gelatin, esculin, or starch. The strain was urease, acid phosphatase, and arginine dihydrolase positive. It was catalase, oxidase, H(2)S, and indole negative. The major products of glucose fermentation were butyrate and lactate. Its mol% G+C was 51.2. The major cellular fatty acids were C(16:0) DMA, C(16:0), and C(16:0) aldehyde. The structural type of cell wall peptidoglycan was suggested to be A1gamma. The isolate was susceptible to beta-lactam, cefem, and macrolide antibiotics and resistant to aminoglycoside and quinolone antibiotics. The bacterium was related to Eubacterium ramulus ATCC29099(T), Eubacterium rectale ATCC33656(T), and species of the genus Roseburia, but the highest 16S rRNA gene similarity to these described species was only 94.4%, consistent with its being classified as a novel genus. Based on the above, the isolate, named strain SY8519, was identified as belonging to a novel genus in the Clostridium rRNA cluster XIVa.
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PMID:Characterization of an O-desmethylangolensin-producing bacterium isolated from human feces. 1990 24