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:3.5.1.5 (urease)
7,257 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ability of casein in the form of colloidal-sized casein micelles to modulate the phase separation of calcium phosphate during milk secretion is adapted to produce nanometre-sized particles of calcium phosphate stabilized by a casein phosphopeptide (nanoclusters). The nanoclusters were prepared from an undersaturated solution of salts and the peptide by raising the pH homogeneously from about 5.5 to 6.7 with urea plus urease. Chemical analysis and IR spectroscopy showed that they comprise an amorphous dicalcium phosophate bound to the phosphopeptide. Multinuclear NMR spectroscopy of the cluster solutions showed that the small ions and free peptide in the solution were in a state of dynamic exchange with the nanoclusters. The peptide is linked to the calcium phosphate through its sequence of phosphorylated residues, but, in a proportion of adsorbed conformational states, the termini retain the conformational freedom of the unbound peptide. The ability of casein to form nanoclusters in milk suggests a more general mechanism for avoiding pathological calcification and regulating calcium flow in tissues and biological fluids exposed to or containing high concentrations of calcium.
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PMID:Ability of a beta-casein phosphopeptide to modulate the precipitation of calcium phosphate by forming amorphous dicalcium phosphate nanoclusters. 861 55

Growth of the yeast Phaffia rhodozyma was carried out in a simplified medium based on less expensive nutrient sources, such as diluted sugar cane juice, urea, and sodium phosphate. The usual content of the astaxanthin, an oxygenated pink carotenoid useful for fish flesh staining, was improved along with with good cell yields (respective values of > 1300 micrograms/g cells and > 5 g cells/L were observed). Yeast invertase and urease must therefore play an important role in the implementation of low-cost culture media.
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PMID:Culture of the astaxanthinogenic yeast Phaffia rhodozyma in low-cost media. 866 8

A protein fold recognition method was tested by the blind prediction of the structures of a set of proteins. The method evaluates the compatibility of an amino acid sequence with a three-dimensional structure using the four evaluation functions: side-chain packing, solvation, hydrogen-bonding, and local conformation functions. The structures of 14 proteins containing 19 sequences were predicted. The predictions were compared with the experimental structures. The experimental results showed that 9 of the 19 target sequences have known folds or portions of known folds. Among them, the folds of Klebsiella aerogenes urease beta subunit (KAUB) and pyruvate phosphate dikinase domain 4 (PPDK4) were successfully recognized; our method predicted that KAUB and PPDK4 would adopt the folds of macromomycin (Ig-fold) and phosphoribosylanthranilate isomerase:indoleglycerol-phosphate synthase (TIM barrel), respectively, and the experimental structure revealed that they actually adopt the predicted folds. The predictions for the other targets were not successful, but they often gave secondary structural patterns similar to those of the experimental structures.
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PMID:Assessment of a protein fold recognition method that takes into account four physicochemical properties: side-chain packing, solvation, hydrogen-bonding, and local conformation. 871 Aug 29

We investigated the effects of weak to moderate urease hydrolysis by optional urease-positive microorganisms in an artificial urine model enriched with calcium phosphate and calcium oxalate in respect of calcium stone formation. The incubation experiments were performed using a discontinuously running fermenter device to simulate the urinary system. The kinetics of cell division rates, pH and ammonium ion production were measured and correlated to crystallite appearance in the incubation medium. Qualitative analyses of the sediments revealed apatite. Investigations using light microscopy and scanning electron microscopy (SEM) confirmed the matrix effect of bacterial glycoproteins. It was shown that initiation of calcium oxalate stone formation is in all probability equally determined by matrix effects and by heteronuclear crystallization if the urinary tract is infected by optional urease-positive bacteria. When urinary inorganic phosphate is present, calcium phosphate nidi are always initially formed, and may subsequently be coated by calcium oxalate.
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PMID:Potential contribution of optional urease-positive bacteria to idiopathic urinary calcium stone formation. II. Microlith formation kinetics in a fermenter model of the urinary tract infected by optional urease-positive microorganisms. 874 Sep 75

Renal tubular acidosis (type I) is characterized by alterations that lead to disturbed acidification in the tubule. As a result of these alterations, the excretion of uromucoid (formed in the distal tubule), citrate and glycosaminoglycan (GAG) is considerably reduced. There have been numerous investigations on changes in urine pH, citrate and calcium, but few, if any studies on the excretion of uromucoid and GAG. Apart from calcium, phosphate, pH and urease, the present study investigated the excretion of uromucoid, citrate and GAG in a collective of 41 stone patients with renal tubular acidosis (type I). We found that uromucoid excretion was reduced on 90.5%, GAG in 72.2% and citrate in 96% of cases. The reduction of uromucoid excretion in particular is characteristic of RTA I, and it has the function of a marker.
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PMID:[The significance of citrate, uromucoid and GAG for diagnosis of renal tubular acidosis in patients with urinary calculi]. 884 53

The function of UreC, the product of a 1,335-bp-long open reading frame upstream from the urease structural genes (ureAB) of Helicobacter pylori, was investigated. We present data showing that the ureC gene product is a phosphoglucosamine mutase. D. Mengin-Lecreulx and J. van Heijenoort (J. Biol. Chem. 271:32-39, 1996) observed that UreC is similar (43% identity) to the GlmM protein of Escherichia coli. Those authors showed that GlmM is a phosphoglucosamine mutase catalyzing interconversion of glucosamine-6-phosphate into glucosamine-1-phosphate, which is subsequently transformed into UDP-N-acetylglucosamine. The latter product is one of the main cytoplasmic precursors of cell wall peptidoglycan and outer membrane lipopolysaccharides. The present paper reports that, like its E. coli homolog glmM, the H. pylori ureC gene is essential for cell growth. It was known that growth of a lethal conditional glmM mutant of E. coli at a nonpermissive temperature can be restored in the presence of the ureC gene. We showed that complete complementation of the glmM mutant can be obtained with a plasmid overproducing UreC. The peptidoglycan content and the specific phosphoglucosamine mutase activity of such a complemented strain were measured; these results demonstrated that the ureC gene product functions as a phosphoglucosamine mutase. Homologs of the UreC and GlmM proteins were identified in Haemophilus influenzae, Mycobacterium leprae, Clostridium perfringens, Synechocystis sp. strain PCC6803, and Methanococcus jannaschii. Significant conservation of the amino acid sequence of these proteins in such diverse organisms suggests a very ancient common ancestor for the genes and defines a consensus motif for the phosphoglucosamine mutase active site. We propose renaming the H. pylori ureC gene the glmM gene.
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PMID:The Helicobacter pylori ureC gene codes for a phosphoglucosamine mutase. 917 91

A voltammetric urea-sensing electrode was prepared by combining a lipid-attached urease layer with a 2,5-dihydroxythiophenol-modified gold electrode. A self-assembled monolayer of dihydroxythiophenol was prepared on the gold surface by soaking the electrode into an ethanolic solution containing the modifier. A layer of the lipid-attached enzyme and that of acetyl cellulose overcoat were successively made on the dihydroxythiophenol-modified electrode by applying a dip-coating procedure. The addition of urea in a test solution (10 mM phosphate buffer, pH 7.0) brought about an increase of pH near the urease layer. The pH shift accompanied a negative shift of the anodic peak, which corresponded to the electro-oxidation of dihydroxyphenol moiety to form quinone, on the linear sweep voltammograms for the urease/dihydroxythiophenol electrode. The concentration of urea (0.2-5 mM) could be determined by measuring the electrode current at -0.05 V versus Ag/AgCl from the voltammogram. The electrode was applied to the determination of urea in human urine; the measurement of electrode current at such a low potential provided the urea determination without any electrochemical interference from L-ascorbic acid and uric acid.
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PMID:Voltammetric enzyme sensor for urea using mercaptohydroquinone-modified gold electrode as the base transducer. 917 17

The effect of concentration of acetohydroxamic acid (AHA) on inhibition of jack bean urease in phosphate buffer, pH 7.0, at 25 degrees C, was studied. The measurements were performed at urease concentration of 2.5 mg/100 cm3 for concentrations of urea and AHA ranging in the range of 2-50 mmol dm-3 and 0.25-10 mmol dm-3, respectively. The reactions were monitored by two techniques: analytical and enthalpimetric. For the analytical technique the growth of ammonia concentration in the course of the reaction was determined. From the recorded progress curves the following parameters were calculated for each inhibitor concentration: the initial reaction rate, the steady-state rate and the inversion constant. From these parameters the inhibition constants of the initial and steady-state stages of the reaction, Ki and Ki, were calculated. The former constant did not change whereas the latter one proved to decrease quickly with an increase in inhibitor concentration. This behaviour resulted from the fact that the inactive complex EI was not a product of internal inversion but was formed in the reaction: 2/3I + EI-->(EI.2/3I). The dissociation constant of this complex is equal to about 0.3 x 10(-3) (mol dm-3)2/3.
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PMID:The enthalpimetric determination of inhibition constants for the inhibition of urease by acetohydroxamic acid. 924 59

An aggregometer technique was used to study urease-induced crystallizations in synthetic urine and human urine from healthy subjects and patients with chronic spinal cord injuries. The two different phases of crystallization, calcium phosphate and magnesium ammonium phosphate, were easily evaluated with a single assay using this technique. The crystallization of calcium phosphate and magnesium ammonium phosphate varied markedly among the different urine specimens after incubation with urease. The turbidity curves from human urine were divided into four patterns. We assumed that the variations in the patterns of the turbidity curves appeared to be mainly due to differences in the composition of the urine and in the original pH, and that the calcium and magnesium concentrations were very important in the urinary constituents.
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PMID:Urease-induced crystallizations of calcium phosphate and magnesium ammonium phosphate in synthetic urine and human urine. 928 35

Urease possesses a dinuclear nickel active site with the metals bridged by a carbamylated lysine residue. In vitro activation of apoprotein (Apo) is achieved by incubation with Ni(II) and bicarbonate as a source of CO2. Analogues of CO2 and bicarbonate were examined for their effects on the Apo activation process. While SO2 had little effect, CS2 was shown to inhibit Apo activation via its ability to substitute for CO2 to yield an inactive dithiocarbamate-containing protein. Sulfur-to-Ni charge-transfer transitions arising from this species yielded an electronic absorption band at 324 nm with a shoulder at 382 nm. Borate, sulfate, phosphate, and molybdate had essentially no effect on Apo activation and did not substitute for bicarbonate, while treatment of Apo with Ni(II) plus vanadate led to the production of active urease containing two Ni and one V per active site. Vanadate-dependent activation of Apo resembled the normal activation process in terms of concentration of anion required, optimal pH, and incubation time needed. Furthermore, the UV-visible spectrum, maximal specific activity [386 +/- 26 U.(mg of protein)-1], Km (1.83 +/- 0.20 mM urea), and pH dependence for the vanadate-containing urease were essentially identical to properties observed for bicarbonate-activated enzyme. Vanadate-activated Apo is proposed to possess a vanadylated lysine that bridges the two Ni ions comprising its metallocenter.
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PMID:Substitution of the urease active site carbamate by dithiocarbamate and vanadate. 939 39


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