Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two aqueous extracts of human faeces were prepared from a healthy male donor and assayed in the SOS Chromotest. Both extracts were positive in microtitre fluctuation tests in Salmonella typhimurium TA100 and Escherichia coli WP2uvrA(pKM101). Differences were observed in the induction factors of these samples when p-nitrophenyl-beta-D-galactopyranoside (p-NPG) and o-nitrophenyl-beta-D-galactopyranoside (o-NPG) were used as substrates for the beta-galactosidase assay in the SOS Chromotest. With one sample, a positive induction factor was reproducibly obtained using p-NPG but not o-NPG. When the bacterial cells were washed with fresh LB broth before enzyme assay, the positive induction factor obtained with p-NPG was reduced to an insignificant level. During the 2-h treatment period, both faecal samples enhanced bacterial growth above that of the zero-dose control. When SOS Chromotest assays were performed with no bacteria or with S. typhimurium TA100 or hisG46 (non-lactose fermenting organisms) in place of E. coli PQ37, it was found that the extracts contained significant levels of endogenous beta-galactosidase and alkaline phosphatase, which, due to their carry-over in the bacterial pellet (after centrifugation to remove the coloured extract) gave rise to the positive induction factor obtained with p-NPG. The results obtained in these experiments indicate that where the SOS Chromotest is applied to biological samples, care should be taken in the interpretation of the data and that a washing step should be included to prevent possible errors occurring due to exogenous enzymes in the sample.
 ...
PMID:Testing human faecal extracts for genotoxic activity with the SOS Chromotest: the importance of controlling for faecal enzyme activity. 314 11

beta-Galactosidase from Alternaria tenius was purified to homogeneity from the cultural fluid using acetone precipitation, ion-exchange chromatography on DEAE-cellulose, adsorption on hydroxylapatite and affinity chromatography on N-(beta-D-galactopyranosyl-thiocarbamoyl)-beta-aminocaproyl-AN-Sepharose 4B. The enzyme homogeneity was demonstrated by ultracentrifugation and polyacrylamide gel electrophoresis with SDS or without it. The specific activity of the homogeneous enzyme is 160 u. per mg of protein; mol. weight as determined by various methods is 142 000-176 000, pI = 4.6, temperature optimum is 60-65 degrees, pH optima for o-nitrophenyl-beta-D-galactopyranoside (o-NPG) and lactose are 3.8--4.4 and 3.6--4.8, respectively. The Km values for o-NPG and lactose are 0.21 . 10(-3) and 6.57 . 10-3 M, respectively. The enzyme is a glycoprotein and contains up to 30% of carbohydrates. EDTA and pCMB have no effect on the beta-galactosidase activity. Galactose acts as a competitive inhibitor, while glucose has no inhibiting effect on the enzyme activity.
 ...
PMID:[Purification and properties of beta-galactosidase from Alternaria tenius]. 679 53

Starting from strain of Salmonella typhimurium purD::lac, 86 exponential cultures were mutagenized with NTG and white or light blue clones on E + ado + Xgal plate were selected as candidates of purRs mutant. Total 66 independent candidate strains were obtained. By assaying their beta-galactosidase activity under the repressed and derepressed conditions, determining their frequency of revertional mutation, Conducting transductional analysis of mutational site and dorminance test, 11 candidates strains were proved to be super-repressor mutants. These mutants are useful for studying the expression of purine biosynthetic gene and relationship between protein structure and function in general.
 ...
PMID:[Expression regulation of purine biosynthetic genes in Salmonella typhimurium. VI. Isolation and characterization of super-repressor mutants]. 975 10

A versatile system consisting of an integrational vector and a bacitracin (Bt)-producing beta-galactosidase (beta-Gal)-negative (Lac-) Bacillus licheniformis TLH strain was constructed to quantify promoter activity and to study gene regulation in a single-copy set-up. The vector pTLH utilizes the promoterless Escherichia coli lacZ gene derived from pQF52 and contains the pBR322 origin of replication and a kanamycin-resistance gene for selection in both B. licheniformis and E. coli. The vector also contains an inner part of the first gene of the Bt synthetase (bts) operon which enables its integration into the bts of B. licheniformis by Campbell-type recombination. This recombination event can be easily tested on a Micrococcus flavus lawn where loss of Bt production, i.e. no clearing zone on the lawn, is indicative of the proper integration. The Lac- B. licheniformis TLH strain was developed by elimination of the natural beta-Gal activity of B. licheniformis strain ATCC 10716 UM12 using NTG mutagenesis.
 ...
PMID:Construction of a single-copy integration vector and its use to study gene expression in Bacillus licheniformis. 978 6