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

A study was implemented to quantitate the hydrolase and transgalactosylase activities of beta-galactosidase (E. coli) with lactose as the substrate and to investigate various factors which affect these activities. At low lactose concentrations the rate of galactose production was equal to the rate of glucose production. The rate of galactose production relative to glucose, however, dropped dramatically at lactose concentrations higher than 0.05 M and production of trisaccharides and tetrasaccharides began (galactose/glucose ratios of about 2:1 and 3:1, respectively, were found for these two types of oligosaccharides). At least five different trissacharides were formed and their patterns of formation showed that they probably utilized both lactose and allolactose as galactosyl acceptors. Allolactose was produced in amounts proportional to glucose at all lactose concentrations (ratios of allolactose/glucose were about 0.88). Analyses of various data, including a reaction analyzed at very early times, showed that the major means of production of allolactose (and the only means initially) was the direct enzymatic transfer of galactose from the 4 position to the 6 position of the glucose moiety of lactose without prior release of glucose from the enzyme. It was shown, however, that allolactose could also be formed in significant quantities by the transfer of galactose to the 6 position of free glucose, and also by hydrolysis of preformed trisaccharide. A mechanism which fits the initial velocity data was proposed in which the steps involving the formation of an enzyme-gallactose-glucose complex, the formation and breakage of allolactose on the enzyme, and the release of glucose all seem to be of roughly equal magnitude and rate determining. Various factors affected the amounts of transgalactosylase and hydrolase activities occurring. At high pH values (greater than 7.8) the transgalactosylase/hydrolyase activity ratio increased dramatically while it decreased at low pH values (less than 6.0). At mid pH values the ratio was essentially constant. The absence of Mg2+ caused a large decrease in the transgalactosylase/hydrolase activity ratio while the absence of all but traces of Na+ or K+ had no effect. The anomeric configuration of lactose altered the transgalactosylase/hydrolase activity ratios, alpha-Lactose resulted in a decrease of allolactose production (transgalactosylase activity) relative to hydrolase activities (glucose production) while beta-lactose had the opposite effect.
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PMID:A quantitation of the factors which affect the hydrolase and transgalactosylase activities of beta-galactosidase (E. coli) on lactose. 0 22

Cells of Lactobacillus bulgaricus, Escherichia coli, and Kluyveromyces (Saccharomyces) lactis immobilized in polyacrylamide gel beads retained 27 to 61% of the beta-galactosidase activity of intact cells. Optimum temperature and pH and thermostability of these microbial beta-galactosidases were negligibly affected by the immobilization. Km values of beta-galactosidase in immobilized cells of L. bulgaricus, E. coli, and K. lactis toward lactose were 4.2, 5.4, and 30 mM, respectively. Neither inhibition nor activation of beta-galactosidase in immobilized L. bulgaricus and E. coli appeared in the presence of galactose, but remarkable inhibition by galactose was detected in the case of the enzyme of immobilized K. lactis. Glucose inhibited noncompetitively the activity of three species of immobilized microbial cells. These kinetic properties were almost the same as those of free beta-galactosidase extracted from individual microorganisms. The activity of immobilized K. lactis was fairly stable during repeated runs, but those of E. coli and L. bulgaricus decreased gradually. These immobilized microbial cells, when introduced into skim milk, demonstrated high activity for converting lactose to monosaccharides. The flavor of skim milk was hardly affected by treatment with these immobilized cells, although the degree of sweetness was raised considerably.
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PMID:Hydrolysis of lactose by immobilized microorganisms. 1 9

The hydrolysis of o-nitrophenyl-beta-D-galactopyranoside (ONPG) by BAL-31, a marine Pseudomonas that acts as a host for bacteriophage PM2, was studied with intact cells and with cell-free extracts. A transport system for ONPG in whole cells and a beta-galactosidase activity in extracts were evident for cells grown on lactose minimal medium. It was found that the addition of isopropylthio-beta-D-galactopyranoside (IPTG) to cells growing in rich medium induced an ONPG hydrolytic activity detectable in cell extracts but cryptic in whole cells. The existence of a transport system for IPTG, which remained cryptic for ONPG, became apparent from studies of the rates of induction of beta-galactosidase as a function of cell mass at different concentrations of IPTG. The main properties of beta-galactosidase and the lactose transport system of BAL-31 were studied in terms of how they were affected by pH, temperature, or by the presence of several sugars. IPTG competitively inhibits the hydrolysis of ONPG by cell extracts. In cells pregrown on lactose, IPTG slightly inhibits the transport of ONPG. Glucose, and with less efficiency lactose, also inhibits the hydrolysis of ONPG in cell extracts. The growth of cells on lactose minimal medium was inhibited by the addition of IPTG. A mechanism for this inhibition and for the inhibition of ONPG transport by IPTG is discussed.
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PMID:Induction and general properties of beta-galactosidase and beta-galactoside permease in Pseudomonas BAL-31. 1 11

Responses of Rhizoctonia solani to herbicides in soil cultures were assessed by measuring soil enzyme activity and other growth-related factors. Both beta-galactosidase (EC 3.2.1.23) and phosphatase (EC 3.1.3.1.3.1.3.2) activities were highly correlated with amounts of mycelium in soil. Both enzyme activities were reduced significantly by either fluometuron or prometryn at 40 microgram/g of soil; the pathogen was more distinctly suppressed by fluometron and showed a stronger tendency to overcome the effects of prometryn with time. Inhibition was also reflected in reduced ultilization of glucose and less CO2-C evolved. Except for an increase in beta-galactosidase activity in the presence of 1 microgram fluometuron, low levels of either herbicide had little effect on the pathogen.
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PMID:Effects of the herbicides fluometuron and prometryn of Rhizoctonia solani in soil cultures. 1 60

Five different carbon sources were examined for their ability to control synthesis of heat-stable enterotoxin (ST) by enterotoxigenic (ENT+) Escherichia coli grown in either a defined medium containing four amino acids or a minimal salts medium. No ST activity was observed when D-glucose, D-gluconate, and L-arabinose were added separately to the defined medium, whereas glycerol and pyruvate decreased toxin levels. Similar results were obtained using a minimal salts medium, except with pyruvate, which did not support growth. Inhibition of ST synthesis by D-glucose was overcome by the addition of 3 X 10(-3) M cyclic adenosine 3',5'-monophosphate. Glucose repression of beta-galactosidase synthesis under conditions optimal for inhibition of ST synthesis was also reversed by exogenous cyclic adenosine 3',5'-monophosphate in the presence of the inducer isopropyl-beta-D-thiogalactopyranoside. The data suggest that control mechanisms for the synthesis of plasmid gene products of bacterial pathogens are similar to those exerted on the host chromosome.
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PMID:Repression of heat-stable enterotoxin synthesis in enterotoxigenic Escherichia coli. 2 Apr 4

Human fetal tissues derived from prostaglandin-induced abortuses (9--18 wk fertilization age) have been utilized to evaluate sphingolipid composition and catabolism. Sphingolipid composition (lipid-hexose, sulfatide, and lipid-bound NANA) was assessed in fetal brain. Sphingolipid catabolism was evaluated in fetal lung and brain through the measurement of relevant acid hydrolases (arylsulfatase A, beta-galactosidase, and hexosaminidase). During the fetal period studied, the parameters of sphingolipid composition revealed variability but no consistent pattern of change. Each acid hydrolase was readily detected. Enzyme specific activities revealed no variation during the 9 fetal wk studied. Cellulose acetate electrophoresis yielded the anticipated isoenzyme patterns for each acid hydrolase with little variation during the period of study. The compositional values support current concepts of cerebral development during this period of fetal life. Together with the catabolic analyses, these studies provide normative data relative to the assessment of metabolic abnormalities during this period of fetal development.
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PMID:Sphingolipid composition and catabolism in human fetal tissues. 3 Dec 73

Mice undergoing graft-versus-host reaction, skin grafting, and inoculation with tumor cells were tested for nonspecific resistance by intravenous challenge with Listeria monocytogenes. Peritoneal exudate macrophages from mice treated in a similar manner were tested in vitro for increased degradation of [1-14C]glucose, ability to degrade antigen/antibody complexes, ability to inhibit intracellular growth of listeria, and staining for beta-galactosidase. There was good correlation between in vivo resistance towards L. monocytogenes and in vitro inhibition of intracellular growth. There was also good correlation between increase in beta-galactosidase and in vivo resistance in mice undergoing a graft-versus-host-reaction.
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PMID:Correlation between in vivo and in vitro functional tests for activated macrophages. 3 98

A general method has been developed for determining the rate of entry of lactose into cells of Escherichia coli that contain beta-galactosidase. Lactose entry is measured by either the glucose or galactose released after lactose hydrolysis. Since lactose is hydrolyzed by beta-galactosidase as soon as it enters the cell, this assay measures the activity of the lactose transport system with respect to the translocation step. Using assays of glucose release, lactose entry was studied in strain GN2, which does not phosphorylate glucose. Lactose entry was stimulated 3-fold when cells were also presented with readily metabolizable substrates. Entry of omicron-nitrophenyl-beta-D-galactopyranoside (ONPG) was only slightly elevated (1.5-fold) under the same conditions. The effects of arsenate treatment and anaerobiosis suggest that lactose entry may be limited by the need for reextrusion of protons which enter during H+/sugar cotransport. Entry of omicron-nitrophenyl-beta-D-galactopyranoside is less dependent on the need for proton reextrusion, probably because the stoichiometry of H+/substrate cotransport is greater for lactose than for ONPG.
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PMID:Metabolic control of lactose entry in Escherichia coli. 9 73

The physiological basis of the Eijkman elevated-temperature test for differentiating fecal from nonfecal coliforms was investigated. Manometric studies indicated that the inhibitory effect upon growth and metabolism in a nonfecal coliform at 44.5 degrees C involved cellular components common to both aerobic and fermentative metabolism of lactose. Radioactive substrate incorporation experiments implicated cell membrane function as a principal focus for temperature sensitivity at 44.5 degrees C. A temperature increase from 35 to 44.5 degrees C drastically reduced the rates of [14C]glucose uptake in nonfecal coliforms, whereas those of fecal coliforms were essentially unchanged. In addition, relatively low levels of nonfecal coliform beta-galactosidase activity coupled with thermal inactivation of this enzyme at a comparatively low temperature may also inhibit growth and metabolism of nonfecal coliforms at the elevated temperature.
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PMID:Fecal coliform elevated-temperature test: a physiological basis. 10 58

The level of penicillin production in the presence of whale oil was shown to be higher. The stimulating effect of the oil was connected with accumulation of large biomass rather than with its specific effect on the biosynthesis. At the beginning of the process the oil eliminated the biomass accumulation lag-phase connected with beta-galactosidase repression by glucose. During the second part of the fermentation process the oil acclerated the culture growth in the presence of lactose. The rate of the oil consumption calculated for carbon was higher than that of the lactose utilization. The presence of the oil in the medium did not prevent the lactose consumption.
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PMID:[Physiological role of fats in the process of penicillin biosynthesis]. 10 53


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