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)

A system is proposed for haemodialysis which involves both dialysis and adsorption. The blood compartment is separated by a membrane from a compartment containing adsorbents and ion exchangers under reduced pressure. Urea is broken down by urease adsorbed on an ion exchanger. The ammonia produced is pumped out and the rest of the unwanted substances are bound to the adsorbing materials. The geometry and principles governing the operation of the device obviate the use of circulating dialysate fluid. Preliminary results from in vitro experiments with such a system are reported and the possibility of using this system clinically is discussed.
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PMID:A possible new sorbent dialyser for haemodialysis. 97 13

A direct enzymatic micromethod (sample volume, 3mul) has been adapted to the centrifugal analyzer (ENI-GEMSAEC) for measurement of urea in plasma and urine. The method is based on urease (urea amidohydrolase, EC3.5.1.5)/glutamate dehydrogenase [l-glutamate:NAD(P)+oxidoreductase (deaminating), EC1.41.3] coupled reactions, and uses a two-point fixed-time (t(1)=20s,t(2)=50s)kinetic scheme for monitoring the rate of comsumption of NADH at 340 nm. Sensitivity and precision of the method are excellent,and results compare well with those from a commonly used continuous-flow method.
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PMID:Direct enzymatic determination of urea in plasma and urine with a centrifugal analyzer. 97 5

The determination of the constant of the urea fission rate and study of the temperature dependence (activation energy) of the urease activity on warm- and cold-blooded animals in Ascaris suum and Contracaecum aduncum were undertaken. It has been shown that the constant of the urea fission rate in C. aduncum is more than an order of magnitude higher than that in A. suum. At a temperature of 17 degrees the rate of this process in C. aduncum changes but little while in A. suum it practically ceases. On the contrary, at 47 degrees the urease ferment activity in A. suum increases considerably while in C. aduncum the process rate does not rise as compared to that at 37 degrees. The subsequent calculations of the energy activation have shown that a certain adaptation to definite conditions of ferments functioning can take place.
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PMID:[Effect of the temperature regimen on the kinetic and thermodynamic functions of the enzyme urease in the helminths of warm-blooded and cold-blooded animals]. 98 2

Urease obtained from seeds of Citrullus vulgaris fruits has been studied under three points of view: a) the effect of the urea analogs acetamide and hydroxi-urea on the enzyme kinetic b) the action of the sulfhydryl reagents and the reactivation agents on the enzyme c) the effect of X-rays and the protective action of the cysteamine. The Berthelot reaction for the determination of the liberated NH3 was used enzyme activity. Acetamide has no effect on urease kinetic. Hidroxy-urea which produces a typical green color when it is mixed with the Berthelot reagents at high concentrations, when properly diluted acts a aompetitive inhibitor of urease. Spectrophotometric experiments suggest that the studied urease decomposes hydroxi-urea with liberation of hydroxilamine. The sulphydril reagent, p-hydroxi-mercuribenzoate inhibits the enzime. Cysteine and dithiotreitol reactivate the enzyme activity in no more then 50% even when excess of the substances is used. Probably only in the first step of the urea hydrolysis, the enzyme behaves as a typical SH-enzyme. Urease is very sensitive to X-rays. Cysteamine acts as a protective agent of the enzyme. Dithiotreitol reinforces this protective action. This effect is clearly observed when the Fisbein catalytic method for urease is employed.
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PMID:[Studies on urease from the seeds of Citrullus vulgaris: action of chemical agents and ionizing radiations]. 103 92

A chemically-defined medium was developed which supported growth of Streptococcus faecium and permitted synthesis of urease. This streptococcus cannot utilize ammonia and needs a complex medium, but its requirements are probably provided in the rumen. The specific activity of urease was inversely related to growth and in no medium was there high growth and high urease activity. Anaerobic culture and the presence of urea in the medium were essential for urease activity, but not for growth.
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PMID:A chemically-defined medium for the growth of a ureolytic strain of Streptococcus faecium. 103 71

Nitrogen-free analogues of essential amino acids, when administered with those essential amino acids for which analogues are ineffective or unavailable, exert three actions that may be beneficial in protein-deficient or protein-intolerant subjects. First, they bring about an increase in the concentrations of essential amino acids in the blood at the expense of the concentrations of certain non-essential amino acids, notably alanine and glutamine. This effect is most readily demonstrated in children with congenital defects of the urea cycle enzymes, but can also be seen during daily therapy of adults with portal-systemic encephalopathy. Second, these compounds promote nitrogen balance through their suppressive effect on urea synthesis (an effect not attributable to re-utilization of ammonia derived from urease action in the gut). This action is demonstrable in obese subjects who are already conserving nitrogen maximally at the end of a prolonged fast and can also be shown in the first week of fasting when the branched-chain keto acids alone are administered. In both situations, improved nitrogen conservation persists long after the analogues are metabolized, suggesting enzyme adaptations. In chronic uremics, nitrogen balance can be maintained in some (but not all) patients on very low nitrogen intakes. Third, these mixtures may delay or reverse the progressive decline in glomerular filtration rate characteristic of chronic renal failure in some cases: thus, for example, 5 of 6 patients taken off chronic dialysis have maintained lower serum urea concentrations without evidence of protein malnutrition for periods of 2-24 months.
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PMID:Evidence for an anabolic action of essential amino acid analogues in uremia and starvation. 107 39

This is the first report of a naturally occurring Salmonella that is urea positive. The strain was identified as Salmonella cubana and it was typical in all biochemical, serological, and bacteriophage reactions, except that is produced urease strongly.
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PMID:Unusual Enterobacteriaceae: a Salmonella cubana that is urease positive. 110 Jun 46

Male rats were fed laboratory chow or a purified L-amino acid diet containing 11.2 or 5.6 g arginine/kg. Hyperammonemia was produced by injection of crystalline jackbean urease. Control animals were injected with saline or inactivated urease. Rats injected with 55 U urease activity/kg body wt (an LD50 dose) exhibited acute signs of hyperammonemia and elevated orotate and citrate in their urine. Plasma glucose, lactate, citrate, and alpha-ketoglutarate concentrations were also markedly elevated. Three injections of active urease (10 U/kg body wt) given at intervals of about 10 h produced hyperammonemia, which persisted for 25 h after the first injection. Blood glucose and ammonia concentrations were increased 2.6- and 22-fold, respectively, when compared with controls. Total urinary citrate excretion for 25 h was 371 mueq for active urease-injected rats compared with 62 mueq for rats injected with inactivated urease. Rats fed a purified amino acid diet containing 5.6 g arginine/kg excreted greater quantities of urea, citrate, and orotic acid than rats fed 11.2 g arginine/kg of diet. Injection of active urease increased citrate excretion by rats fed either concentration of dietary arginine. Changes produced with active urease were not observed if inactivated urease was injected.
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PMID:Citric, orotic, and other organic acids in rats injected with active or inactive urease. 111 48

An enzymatic, fluorometric method is described for determination of serum urea on silicone-rubber pads. In this method, the reagents are lyophilized on the surface of the pads, NADH on one side and a mixture of urease, glutamate dehydrogenase, and alpha-ketoglutarate on the other. The rate of disappearance of NADH fluorescence at 460nm (excitation wavelength, 340 nm) is monitored and related to serum urea concentration. The calibration curve is linear to 250 mg of urea per liter. The method affords a rapid, simple, and inexpensive means for urea assay, the results of which correlate well with automatic diacetyl monoxime method (correlation coefficient, 0.998).
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PMID:Enzymatic determination of serum urea on the surface of silicone-rubber pads. 111 80

In the unicellular green alga Chlamydomonas reinhardi (strain y-1), synthesis of the enzymes required for urea hydrolysis is under substrate induction control by urea and under end product repression control by ammonia. Hydrolysis of urea if effected by the sequential action of the discrete enzymes urea carboxylase and allophanate lyase, collectively called urea amidolyase. The carboxylase converts urea to allophanate in a reaction requiring biotin, adenosine 5'-triphosphate, and Mg2+. The lyase hydrolzyes allophanate to ammonium ions and bicarbonate. Neither activity is present in more than trace amounts when cultures are grown with ammonia or urea plus ammonia, or when they are starved for nitrogen for 8 h. Urea in the absence of ammonia induces both activities 10 to 100 times the basal levels. Addition of ammonia to an induced culture causes complete cessation of carboxylase accumulation and an 80% depression of lyase accumulation. Ammonia does not reduce urea uptake by repressed cells, so it does not prevent induction by the mechanism of inducer exclusion. The unicellular green alga Chlorella pyrenoidosa (strain 3 Emerson) also has discrete carboxylase and lyase enzymes, but only the carboxylase exhibits metabolic control.
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PMID:Metabolic control of urea catabolism in Chlamydomonas reinhardi and Chlorella pyrenoidosa. 111 94


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