Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “UREASE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44Linked to original sources
PubMed2006

Synthetic peptides mimicking antigenic epitope of Helicobacter pylori urease.

Short peptides resembling the Helicobacter pylori urease antigen (UreB F8 Ser-Ile-Lys-Glu-Asp-Val-Gln-Phe) with deleted aspartic acid and glutamic acid residues, anchored through a triazine linker via the N-terminal moiety to cellulose plate were prepared. The peptides were used for binding of antibodies from sera of patients with medically confirmed atherosclerosis. Recognition of the peptides was also tested with anti-Jack beans urease antibodies. The important role of a Gly-Gly spacer separating the peptides from the cellulose support was shown. Different patterns of binding of antibodies from H. pylori infected patients and anti-Jack bean urease antibodies were observed only in the case of pentapeptides. The peptide Gly-Gly-Leu-Val-Phe-Lys-Thr was recognized by most of the tested sera.

Aspartic Acid↗
PubMedDate not supplied

The potential of a microencapsulated urease-zeolite oral sorbent for the removal of urea in uremia.

Although successful in reducing urea levels, the use of oral microcapsules containing a urease-silica adduct and a zirconium phosphate ion exchanger result in a number of problems, including a negative calcium balance. In this study, it is demonstrated that the use of microcapsules containing a urease-zeolite preparation may be a potential route to urea removal. The use of zeolite ion exchangers, and zeolite W in particular, can alleviate the problems encountered with zirconium phosphate. Unlike zirconium phosphate, zeolite W is nonselective toward calcium ions and is stable at the high pH found in the intestinal tract. Zeolite W, when present in the sodium form, has a high ammonium capacity of 3.6 mEq NH4+/g zeolite under simulated intestinal conditions; its reactivity to ammonium is also higher. The application of enzyme envelopes to zeolite particles is a novel immobilization procedure that does not involve the use of colloidal silica and can reduce the amount of ingested material by as much as 25%. The current in vitro study shows that cellulose acetate butyrate microcapsules, containing a urease-zeolite preparation, remove up to 80% of urea in less than 1 hour. These microcapsules can be dried and retain activity when sealed in a jar at 4 degrees C.

Aluminum Silicates↗
PubMed1990

[A method for determining urea by using immobilized urease].

An available method was developed for manual measurements of urea in biological fluids with the use of urease immobilized in sepharose gel. The suggested technique is more reagent-saving (the same reagent may be used for up to 500 times), 3-6-fold more rapid, and twice more sensitive than the routine phenolhypochlorite method with soluble urease. The method is characterized by a high analytical reliability, its results are in high correlation with the soluble urease procedure and with the diacetylmonoxime method (r = 07988 and 0.995, respectively). It is particularly fit for rapid analysis of the urea and convenient for small laboratories.

Enzymes, Immobilized↗
PubMed2006

[Effects of pesticides on soil urease activity].

With simulation test, this paper studied the effects of chlorimuron-ethyl and furadan on the urease activity of six meadow brown soil and black soil samples. The results showed that within the range of test concentrations, these two pesticides could activate the urease activity of test soils, with the largest increment in meadow brown soil and black soil being 46.95% and 39.36% by chlorimuron-ethyl, and 21.08% and 12.70% by furadan, respectively. Quadratic polynomial equation could better describe the relationships between the concentrations of chlorimuron-ethyl and furadan and the activity of soil urease (P < 0.05). Judging from the equations for test pesticides, chlorimuron-ethyl had more significant effect than furadan.

Carbofuran↗
PubMed1991

Identification of the essential cysteine residue in Klebsiella aerogenes urease.

During reaction with [14C]iodoacetamide at pH 6.3, radioactivity was incorporated primarily into a single Klebsiella aerogenes urease peptide concomitant with activity loss. This peptide was protected from modification at pH 6.3 by inclusion of phosphate, a competitive inhibitor of urease, which also protected the enzyme from inactivation. At pH 8.5, several peptides were alkylated; however, modification of one peptide, identical to that modified at pH 6.3, paralleled activity loss. The N-terminal amino acid sequence and composition of the peptide containing the essential thiol was determined. Previous enzyme inactivation studies of K. aerogenes urease could not distinguish whether one or two essential thiols were present per active site (Todd, M. J., and Hausinger, R. P. (1991) J. Biol. Chem. 266, 10260-10267); we conclude that there is a single essential thiol present and identify this residue as Cys319 in the large subunit of the heteropolymeric enzyme.

Amino Acid Sequence↗
PubMed1991

[Diagnosis of Helicobacter pylori colonization of the gastric mucosa. A prospective comparative study of direct test methods and validation of a new urease test].

A prospective study including 119 patients submitted for routine endoscopy of the upper gastrointestinal tract was initiated to compare three commercial biopsy urease tests with regard to sensitivity and specificity in detecting Helicobacter pylori colonization of the gastric mucosa and their reaction velocity. Specific culture, microscopy after staining with methylene-blue, histologic search after modified Giemsa staining and the combined results of culture and histology ("true standard") served as reference methods. The sensitivity and specificity of all three tests were high: Angass urease test 92.0%/97.7%, Telen-Quick test 94.7%/100%, CLO-test 94.7%/100% (analysis of one antrum and one body biopsy in a single test kit). Telen-Quick and CLO-tests reacted faster than the Angass urease test, but a period of 24 hours was necessary for all three tests to detect "true negatives". Histology and microscopy were reliable reference methods concerning sensitivity and specificity, while culture was characterized by inferior sensitivity (78.6%) and high specificity (100%).

Adolescent↗
PubMed1990

Evaluation of urease test, gram stain, culture, and histology in the detection of Campylobacter pylori.

To evaluate the commonly available tests for detection of Campylobacter pylori infection in the human stomach, we prospectively performed endoscopy and biopsy from the antrum of the stomach in 121 consecutive patients. Four tests, including the urease test, Gram stain, culture, and the hematoxylin and eosin (H & E) stain were used to detect the presence of C. pylori. A C. pylori positive was defined by a positive culture or positive results in two of the other three tests. The sensitivity of the urease test, Gram stain, culture, and H & E stain was 95%, 95%, 71%, and 97%, respectively, and the specificity of those tests was 96%, 100%, 100%, and 73%, respectively. For diagnosis, theoretically, all four tests should be performed from the biopsy specimens. In our experience, the culture was less sensitive, and the H & E stain was less specific, while the urease test and Gram stain were more rapid and had high sensitivity and specificity in the detection of C. pylori infection.

Adolescent↗
PubMed1990

Development of urease-chitosan membrane.

Urease was covalently immobilized on glutaraldehyde-pretreated chitosan membrane. The optimum immobilization conditions were determined with respect to glutaraldehyde pretreatment of membranes (concentration and pH of glutaraldehyde solution, time of membrane-glutaral-dehyde reaction) and to reaction of glutaraldehyde-pretreated membranes with urease (concentration and pH of urease solution). The obtained membrane has high enzymatic activity, and can be applied for enzymatic removal of urea e.g. in the treatment of chronic or acute uraemia.

Animals↗
PubMedDate not supplied

Sustained-release of urease from a poloxamer gel matrix.

With the increase of extremely specific polypeptide drugs arising from advances in recombinant DNA techniques, there exists a need with which to optimally deliver these genetically engineered drugs. This results from the normally short circulating half-life of these macromolecules. A well characterized model enzyme, urease, was formulated in a 20, 30, and 35% w/w poloxamer 407 gel matrix and the release profile determined in a membraneless diffusion system (Area = 11.4 cm2) in vitro at 37 degrees C over 8 hours. Polymer release into a pH = 7.0 phosphate buffer receptor phase due to matrix erosion was constant throughout 8 hours and ranged from 1.07% +/- 0.04 cm-2 hr-1 to 0.48% +/- 0.02 cm-2 hr-1 for the 20% w/w and 35% w/w poloxamer gel matrices, respectively. The predominant mechanism governing release of protein from the semisolid, poloxamer 407 gel matrix in vitro was matrix erosion with the cumulative urease released ranging from 89.5% +/- 3.5 after 7 hours (20% w/w, n = 3) to 46.6% +/- 0.3 following 8 hours of released (35% w/w, n = 3), respectively. The percent relative biological activity of the enzyme [(Act.poly/Act.cont)*100] remaining was determined following incubation in a 14% w/w concentration of poloxamer 407 for 8 hours at 4, 22, and 37 degrees C. The percent relative enzyme activity remaining following incubation in the 14% w/w poloxamer 407 solution after 8 hours was not significantly different (p greater than 0.05) between samples incubated at 4 degrees C (94.2% +/- 2.4) and 37 degrees C (89.7% +/- 1.7). Hydrodynamic properties of dilute urease and poloxamer 407 solutions were assessed using viscometry.(ABSTRACT TRUNCATED AT 250 WORDS)

Delayed-Action Preparations↗
PubMed1987

Urease activity of adherent bacteria and rumen fluid bacteria.

In experiments on six sheep fed on a low nitrogen diet (3.7 g N/day), urease (EC 3.5.1.5) activity (nkat X mg-1 bacterial dry weight) 3 h after feeding was found to be highest in the bacteria adhering to the rumen wall (13.25 +/- 2.10), lower in the rumen fluid bacteria (8.96 +/- 1.35) and lowest in the bacteria adhering to feed particles in the rumen (5.69 +/- 2.13). The urease activity of bacteria adhering to the rumen wall and of the rumen fluid bacteria of six sheep fed on a high nitrogen diet (21 g N/day) was significantly lower than in sheep with a low N intake and in both cases was roughly the same (3.81 +/- 1.37 and 3.76 +/- 1.02 respectively); it was lowest in bacteria adhering to feed particles in the rumen (1.92 +/- 0.90). It is concluded from the results that the urease activity of rumen fluid bacteria and of bacteria adhering to the rumen wall and to feed particles in the rumen is different and that it falls significantly in the presence of a high nitrogen intake. From the relatively high ureolytic activity of bacteria adhering to the rumen wall in the presence of a low nitrogen intake it is assumed that this is one of the partial mechanisms of the hydrolysis of blood urea entering the rumen across the rumen wall and of its reutilization in the rumen-liver nitrogen cycle in ruminants.

Animal Feed↗
PubMed1987

[Effect of physiological factors on biosynthesis of urease in Bacillus spp].

In this study, urea was shown to be the inducer of the urease enzyme of the soil isolate Bacillus spp. The extracellular urease enzyme production was repressed in UGT cultures containing ammonia, ammonium chloride or tryptophane and in nutrient broth cultures. The optimal urease production culture conditions were determined as pH: 7.0, 30 degrees C and 150 rpm.

Bacillus↗
PubMedDate not supplied

[Stabilization of native and immobilized urease].

The stability of native and immobilized urease isolated from Staphylococcus saprophyticus was studied at 4 degrees and 25 degrees C. The activity yield was 20% and 1.4% on the enzyme immobilization in albumin gel and latex membrane, respectively. Inactivation of native microbial urease proceeded 10 times slower in the solution containing 1 mM EDTA and 30 mM sodium sulfite. This solution contributed to a great extent to stabilization of immobilized urease both during storage in the phosphate buffer solution and in case of lyophilization.

Enzyme Stability↗
PubMedDate not supplied

[Various properties of urease encapsulated into liposomes].

The enzymic activity of plant urease encapsulated into liposomes from egg lecithin was studied. Liposomes contained 3-5% of the initial enzymic preparation. Incorporation of urease into liposomes increases the permeability of the lecithin membrane for urea. The liposome membrane provides protection of the incorporated material from the inhibitory action of heavy metal ions. Kinetics of the reactions catalyzed by the free enzyme and encapsulated one is different. Km for the encapsulated enzyme is 1 X 10(-3) M and for free urease--4 X 10(-4) M, that is related to limited substrate mass transfer rate and as a result of it due to inhomogeneity of the catalysis proceeding in liposomes.

Hydrolysis↗
PubMed1985

Urease activity of Brucella species.

Examination of the urease activity of 604 brucella strains showed a limited correlation with species. Most strains of B canis, B neotomae and B suis gave a positive urease reaction within 15 minutes, although some exceptions were noted. A substantial proportion of strains of B abortus and B melitensis also hydrolysed urea as rapidly as most B suis strains. Although most B ovis strains were negative to the urease test, 28.9 per cent of those examined gave positive reactions.

Brucella↗
PubMed1979

Studies on urea hydrolysis. Part 2. Effects of some heavy metals on urease activity.

The effect of some heavy metals on the urease activity was studied in a pure system using jack bean urease (JBU). While Mn showed no effect, copper reduced the enzyme activity more than did Zn or Fe at high concentrations (100 ppm). At a low concentration, iron reduced the enzyme activity more than at a high concentration. Inhibition of the urease activity was induced by less than 0.1 ppm Fe, 0.5 ppm Cu, and 10.0 ppm Zn. In the soil, these heavy metals inhibited the JBU in this order: Fe++ greater than Cu++ greater than Zn++. The possibility is discussed of using heavy metals to delay urea hydrolysis in soils.

Copper↗
PubMedDate not supplied

[Choice and selection of a Staphylococcus saprophyticus strain--a urease producer].

A new strain of Staphylococcus saprophyticus was isolated from natural sources. The strain has a higher activity of urease comparing to other cultures producing the enzyme. The strain is referred to as S. saprophyticus L-1. The natural variability of the strain was studied and the population was shown to have only one morphological type of colonies. The homogeneous population reversed to R and S forms after storage under vaseline oil. Although S forms had a lower viability, they produced more urease under the conditions of submerged cultivation than R forms. As the result of selection among S form colonies, three variants which retained the ability to synthesize urease at a high rate upon many passages were isolated.

Air Microbiology↗
PubMed1984

Influence of urease present in non viable organisms on the decline phase of Ureaplasma growth.

Broth cultures infected with ureaplasmas for 48 hrs were unable to support further growth of reinoculated ureaplasmas even when reconstituted with fresh ureaplasma medium. The apparent toxicity of spent cultures was ascribed to the presence of non viable ureaplasmas still containing a fully active urease since all the procedures adopted to abolish or reduce the urease activity restored the ability of these spent cultures to support ureaplasma growth. However, if the cause of the steep decline phase of ureaplasma cells could be reasonably ascribed to the enzymatic activity of urease present in the dead cells, the reasons for the poor field and the low titers achieved by the organisms during the logarithmic phase of growth remain an enigma.

Ammonium Chloride↗
PubMed1984

Urease activity of adherent bacteria in the sheep rumen.

In experiments on six sheep fed on a low protein diet (6.2 g N/day), it was found that the urease activity of the rumen fluid did not change significantly in the first 6 hours after feeding and that it ranged from 45 to 75 nkat.ml-1. The major portion was bound to the bacterial fraction and formed about 70% of total rumen fluid activity. Urease activity determined in food particles with adherent bacteria removed from the rumen before and 3 and 6 hours after feeding ranged from 20 to 26 nkat.g-1 food (wet weight), and on rumen wall samples with adherent bacteria from 30 to 800 nkat per 2.5 cm2 tissue. Again, no significant changes correlated to the time after feeding were found. The results show that urease activity in the sheep rumen is localized on food particles and on rumen wall epithelium with adherent bacteria, as well as in the rumen fluid.

Ammonia↗