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:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The feasibility and efficacy of adding microbial beta-galactosidase enzymes directly to milk at the time of consumption was explored in adult lactose-malabsorbers. The hydrogen breath test, and on one occasion, the rise in blood glucose, were used as indices of the completeness of intraintestinal hydrolysis and absorption of milk lactose. When added to 360 ml of cow milk containing 18 g of lactose, empirical dosages of three beta-galactosidases--one from Kluyveromyces (yeast) and two from Aspergillus (fungal)--had some effectiveness in reducing postprandial H2 excretion, although no in vivo treatment at the dosages chosen was as effective as pre-incubation of the milk in vitro. The yeast enzyme also reduced symptom frequency as compared to intact milk and enhanced postprandial rises in blood glucose. The replacement therapy with exogenous, food-grade beta-galactosidases may provide a useful intervention to reduce lactose malabsorption and milk intolerance in individuals with primary lactase deficiency.
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PMID:Dietary manipulation of postprandial colonic lactose fermentation: II. Addition of exogenous, microbial beta-galactosidases at mealtime. 391 30

The feasibility of enzyme replacement therapy with exogenous, food-grade, microbial enzymes at mealtime to effect intragastrointestinal hydrolysis of the lactose from 360 ml of cow's milk consumed with a solid food meal (breakfast cereals) was investigated in adult Guatemalan lactose-malabsorbers using a hydrogen breath-analysis procedure to quantify the completeness of postprandial carbohydrate absorption. Adding 2 g of a commercial preparation of beta-galactosidase from Kluyveromyces lactis at mealtime to milk taken with a refined cereal (cornflakes) and an unrefined cereal (bran) reduced the production of excess breath H2 attributable to lactose maldigestion to a level not significantly different from that achieved with lactose-prehydrolyzed milk. Sucrase, as expected, had no effect on H2 production. A beta-galactosidase from Aspergillus niger was less effective that the K. lactis enzyme for in vivo hydrolysis. Thus, exogenous betagalactosidases can eliminate lactose malabsorption in lactase-deficient individuals even in the presence of solid foods, allowing lactose intolerant persons to consume milk and dairy products without gastrointestinal discomfort.
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PMID:Effective in vivo hydrolysis of milk lactose by beta-galactosidases in the presence of solid foods. 391 31

The ability of 24 systematically modified analogues of adenosine 3',5'-monophosphate (cAMP) to enhance the synthesis of beta-galactosidase in glucose-repressed Escherichia coli strains KNBL 1001 and cpd- Crookes has been investigated. The properties of the analogues in comparison with cAMP are, with only two exceptions, alike in both strains. Two analogues, 7-deazaadenosine 3',5'-monophosphate (i.e. tubercidin 3',5'-monophosphate) and (Rp)-adenosine 3',5'-monothionophosphate, exhibit higher biological activity than cAMP. The latter analogue is 50-fold more active in both strains. Three analogues showed activities comparable to cAMP, four analogues were less active and 12 analogues were unable to antagonize catabolite repression. Structure-activity correlations showed that the 2'OH-, 3'O-, 5'O-, the negative charge and the 6-amino group cannot be modified without losing biological activity in vivo, while the N-1 and N-7 in adenine are not essential. The interaction with the catabolite gene activator protein is stereoselective for an unmodified axial exocyclic oxygen. The results are compared to those obtained with cAMP analogues in E. coli in vitro and those obtained with the same analogues in protein-kinase systems and Dictyostelium species. The model of McKay et al. [McKay, D.B., Weber, J.T. and Steitz, T.A. (1982) J. Biol. Chem. 257, 9518-9524] proposed for distinct chemical interactions of cAMP with the catabolite gene activator protein is discussed and supplemented by additional hydrogen bond interactions.
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PMID:Investigations on stimulation of lac transcription in vivo in Escherichia coli by cAMP analogues. Biological activities and structure-activity correlations. 631 29

The kinetics for imino hydrogen exchange, at individual base pairs in the DNA sequence corresponding to the lactose operon operator of Escherichia coli, has been examined by NMR saturation recovery measurements as a function of temperature. Three 17-base-pair subsections of the lac operator DNA were chemically synthesized for these studies. The results support our previous observations in the 36-base-pair complete lac operator DNA fragment that has been used in our previous NMR studies. The results indicate faster opening kinetics at a GTG/CAC that is also the site of operator mutations leading to the highest level of constitutive beta-galactosidase synthesis. The GTG/CAC sequence occurs frequently and often symmetrically in prokaryotic and eukaryotic DNA sites where one anticipates specific protein interaction for gene regulation or recombination.
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PMID:Correlation of lac operator DNA imino proton exchange kinetics with its function. 632 23

Mutants of Escherichia coli were isolated in which transcription of the structural genes for hydrogenase (hyd) and for one of the components of formate dehydrogenase (fdh) (of the formate hydrogen-lyase complex) is coupled with that of the lacZ gene. They were--together with lac fusions of the nifH and nifL genes from Klebsiella--used to study regulation by redox control, of the expression of the respective structural genes. The following results were obtained: (i) beta-galactosidase synthesis was fully repressed in the presence of O2 or nitrate (anaerobically), and induced in the absence of an external electron acceptor. Fumarate as terminal electron acceptor only marginally affected nif expression and partially repressed hyd and fdh expression. Redox control of the synthesis of hydrogenase and formate dehydrogenase, therefore, (as well as that of nif) acts at the level of transcription; the size of the redox potential seems to be correlated with the amount of repression; (ii) beta-galactosidase synthesis in the hyd:: lac and fdh::lac fusion strains is induced by formate. At high concentrations formate reverses the repression by nitrate and fumarate but not that by oxygen.
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PMID:On the redox control of synthesis of anaerobically induced enzymes in enterobacteriaceae. 636 66

The addition of microbial beta-galactosidases directly to milk at mealtime represents a potential "enzyme replacement therapy" for primary lactase deficiency. We used the hydrogen breath test as the index of incomplete carbohydrate absorption to assess the efficacy of two enzymes--one from yeast, Kluyveromyces lactis (LactAid), and the other from the fungus Aspergillus niger (Lactase N)--to assist in the hydrolysis of 18 g of lactose in 360 ml (12 oz) of whole milk when consumed by an adult lactose malabsorber. Graded amounts of Lactase N produced, at best, a 53% relative reduction in breath hydrogen excretion, whereas quantitative elimination of excess hydrogen excretion was produced by 1 and 1.5 g of LactAid. A double-blind, controlled, crossover trial was subsequently performed in 50 healthy, unselected Mexican adults, to whom 360 ml of cow's milk was presented in the three forms in a randomized order: intact milk, prehydrolyzed milk, and milk to which 1 g of LactAid was added immediately before consumption. Among the 25 subjects with incomplete carbohydrate absorption with intact milk, adding enzyme 5-min before consumption produced a 62% reduction in breath hydrogen excretion, and symptoms of intolerance were significantly reduced. The feasibility of effective enzyme replacement therapy with a beta-galactosidase from K. lactis is demonstrated.
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PMID:Enzyme replacement therapy for primary adult lactase deficiency. Effective reduction of lactose malabsorption and milk intolerance by direct addition of beta-galactosidase to milk at mealtime. 643 67

Milk lactose is hydrolysed to D-galactose and D-glucose in the small intestine of mammals by the lactase-phlorizin hydrolase complex (LPH, EC 3.2.1.23-62). Lactase activity has broad substrate selectivity and several glycosides are substrates. Recently, using the monodeoxy derivatives of methyl beta-lactoside (1), we have shown the importance of each hydroxyl group in the substrate molecule concerning the interaction with the enzyme. Now we have studied the corresponding O-methyl derivatives, as well as some of the halo derivatives of 1. We have found that the enzyme presents steric restrictions to the recognition of substrates modified in the galactose moiety. In contrast, the binding site for the aglycon part of the substrate is looser. On the other hand, we have previously shown that HO-3' and HO-6 were important for the recognition of the substrate by the enzyme. Now we have found that the corresponding fluorine derivatives are not, or very poorly, recognized. This suggests that the HO-3' and HO-6 participate, as donors, in hydrogen bonds in the interaction with the enzyme.
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PMID:Substrate specificity of small-intestinal lactase: study of the steric effects and hydrogen bonds involved in enzyme-substrate interaction. 764 81

Lactose in yogurt is better absorbed by lactase-deficient subjects than is an equivalent quantity of lactose in milk, presumably because of the microbial activity of the beta-galactosidase present in yogurt. In this study, we describe a process that increases the beta-galactosidase of yogurt 5- to 6-fold and the ability of this high lactase yogurt to enhance lactose absorption in lactase-deficient subjects. These subjects ingested the yogurt meals after a 12-h fast, and lactose malabsorption was determined by measuring breath hydrogen. Breath hydrogen was reduced 39% following ingestion of high lactase yogurt from that after consumption of conventional yogurt, indicating that the high lactase yogurt enhanced lactose absorption. However, the reduction after high lactase yogurt was less than expected, given the 5- to 6-fold increment in beta-galactosidase measured in vitro. In vivo activity of beta-galactosidase requires that the enzyme resist acid denaturation in the stomach. The beta-galactosidase in high lactase yogurt was much less acid resistant than was the beta-galactosidase in conventional yogurt, and the relative inability of high lactase yogurt to enhance lactose absorption was likely due to the destruction of the beta-galactosidase in the stomach.
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PMID:Factors affecting the ability of a high beta-galactosidase yogurt to enhance lactose absorption. 769 33

Expression of the soluble (SH) and membrane-bound (MBH) hydrogenases in the facultatively lithoautotrophic bacterium Alcaligenes eutrophus is dependent on the transcriptional activator HoxA and the alternative sigma factor sigma 54. Deletion analysis revealed that a region 170 bp upstream of the transcriptional start of the SH operon is necessary for high-level promoter activity. Mobility shift assays with DNA fragments containing the SH upstream region and purified beta-galactosidase-HoxA fusion protein isolated from Escherichia coli or authentic HoxA isolated by immunoaffinity chromatography from A. eutrophus failed to detect specific binding. In contrast, A. eutrophus extracts enriched for HoxA by heparin-Sepharose chromatography and ammonium sulfate fractionation produced a weak but discrete shift in the mobility of the target DNA. This effect was not observed with comparable extracts prepared from hoxA mutants. A similar experiment using antibodies against HoxA confirmed that HoxA was responsible for the observed mobility shift. Extracts prepared from a temperature-tolerant mutant of A. eutrophus gave a stronger retardation than did those from the wild type. Unlike the wild type, the hox(Tr) mutant is able to grow with hydrogen at temperatures above 33 degrees C because of a mutation in the regulatory gene hoxA. In this paper, we show that a single amino acid substitution (Gly-468-->Val) in the C-terminal part of HoxA is responsible for temperature tolerance. The SH upstream region also contains sequence motifs resembling the E. coli integration host factor (IHF) binding site, and purified E. coli IHF protein shifted the corresponding indicator fragment.
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PMID:Temperature tolerance of hydrogenase expression in Alcaligenes eutrophus is conferred by a single amino acid exchange in the transcriptional activator HoxA. 773 Feb 67

We have isolated promoters inducible by paraquat, a superoxide radical-generating agent, from Escherichia coli, using promoter-probing plasmid pJAC4 (Y.S. Koh and J.H. Roe, Korean J. Microbiol. 31:267-273, 1993). One promoter clone pqi-5 (pqi denotes paraquat-inducible gene) was mapped at 21.8 min on the E. coli chromosome by using the Kohara phage library. We constructed an operon fusion of the lacZ gene with the pqi-5 promoter to monitor the expression of the gene in the single-copy state. LacZ expression was induced about 7- to 13-fold by 77 to 780 microM paraquat. Other known superoxide generators such as menadione, phenazine methosulfate, and plumbagin also induced the expression of beta-galactosidase in this fusion strain. On the other hand, no significant induction was observed with treatment with hydrogen peroxide, ethanol, and heat shock. Induction of beta-galactosidase was significantly reduced by introducing a delta sox-8::cat or soxS3::Tn10 mutation into the fusion strain, indicating that pqi-5 is a member of the soxRS regulon. A DNA fragment containing the pqi-5 promoter was cloned and sequenced from the Kohara phage E2E5. We identified two pqi-5 open reading frames (ORFs); ORF-A encodes a predicted protein of 342 amino acids, and ORF-B is truncated at the cloning site. The transcription start site from the pqi-5 promoter was determined by primer extension and S1 nuclease protection analyses. Northern (RNA) and S1 analyses indicated that there are two kinds of pqi-5 transcript; one covers ORF-A only and the other covers ORF-A and possibly also ORF-B.
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PMID:Isolation of a novel paraquat-inducible (pqi) gene regulated by the soxRS locus in Escherichia coli. 775 Dec 75


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