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)

Five alginolytic, facultative anaerobic, non-motile bacteria were isolated from the gut of Japanese abalones (Haliotis discus discus, H. diversicolor diversicolor and H. diversicolor aquatilis). Phylogenetic analyses based on 16S rRNA gene and gap gene sequences indicated that these strains are closely related to V. halioticoli. DNA-DNA hybridizations, FAFLP fingerprintings, and phylogenies of gap and 16S rRNA gene sequences showed that the five strains represent two species different from all currently described vibrios. The names Vibrio neonatus sp. nov. (IAM 15060T = LMG 19973T = HDD3-1T; mol% G+C of DNA is 42.1-43.9), and Vibrio ezurae sp. nov. (IAM 15061T = LMG 19970T = HDS1-1T; mol% G+C of DNA is 43.6-44.8) are proposed to encompass these new taxa. The two new species can be differentiated from V. halioticoli on the basis of several features, including beta-galactosidase activity, assimilation of glycerol, D-mannose and D-gluconate.
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PMID:Vibrio neonatus sp. nov. and Vibrio ezurae sp. nov. isolated from the gut of Japanese abalones. 1549 May 53

The regioselectivity of beta-galactosidase derived from Bacillus circulans ATCC 31382 (beta-1,3-galactosidase) in transgalactosylation reactions using D-mannose as an acceptor was investigated. This D-mannose associated regioselectivity was found to be different from reactions using either GlcNAc or GalNAc as acceptors, not only for beta-1,3-galactosidase but also for beta-galactosidases of different origins. The relative hydrolysis rate of Gal beta-pNP and D-galactosyl-D-mannoses, of various linkages, was also measured in the presence of beta-1,3-galactosidase and was found to correlate well with the ratio of disaccharides formed by transglycosylation. The unexpected regioselectivity using D-mannose can therefore be explained by an anomalous specificity in the hydrolysis reaction. By utilizing the identified characteristics of both regioselectivity and hydrolysis specificity using D-mannose, an efficient method for enzymatic synthesis of beta-1,3-, beta-1,4- and beta-1,6-linked D-galactosyl-D-mannose was subsequently established.
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PMID:Regioselectivity in beta-galactosidase-catalyzed transglycosylation for the enzymatic assembly of D-galactosyl-D-mannose. 1550 53

The earlier published and new experimental data are summarized on the properties of the genes encoding the membrane proteins of the DMT family (RhtA (YbiF), EamA (YdeD), YijE, YddG, YedA, PecM, eukaryotic nucleoside phosphate sugar and hexose phosphate transporters), the RhtB/LysE family (RhtB, RhtC, LeuE, YahN, EamB (YfiK), ArgO (YggA), CmaU), as well as some other families (YicM, YdhC, YdeAB, YdhE (NorE)). These proteins are involved in the export of amino acids, purines, and other metabolites from the cell. The expression of most of the genes encoding these proteins is not induced by the substrates they transport but is controlled by the global regulation systems, such as the Lrp protein, and activated by the signal compounds involved in the intracellular communication. The level of expression, assessed in experiments on translational fusion of the corresponding bacterial genes with the beta-galactosidase gene, depends on the growth phase of the bacterial culture, composition of the medium, and some stress factors, such as pH osmolarity or decreased aeration. The efflux of normal cell metabolites is assumed to be the natural function of these proteins. This function may play a role in density-dependent behavior of cell populations (quorum sensing). It may have been enhanced in the course of evolution via specialization of these proteins in the efflux of compounds derived from metabolic intermediates and adjusted to the role of transmitters.
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PMID:[Export of metabolites by the proteins of the DMT and RhtB families and its possible role in intercellular communication]. 1702 77

A novel transglycosylating beta-galactosidase was purified from Enterobacter agglomerans B1. It was a homodimer of approximately 248 kDa. The optimal pH and temperature for oNPGal hydrolysis were 7.5-8.0 and 37-40 degrees C, respectively. The K(m) values for oNPGal and lactose were 0.06 and 114 mM, respectively. The enzyme produced galacto-oligosaccharides in a 38% yield at the lactose concentration of 12.5% (w/v). When using oNPGal as donor, the enzyme was able to catalyze glycosyl transfer to a series of acceptors, including hexose, pentose, beta- or alpha-disaccharides, hexahydroxy alcohol, cyclitol, and aromatic glycosides. This suggested the enzyme to be a potential synthetic tool for preparing galactose-containing chemicals. The gene encoding this enzyme was cloned by degenerate PCR and TAIL-PCR. It revealed an ORF of 3090 nucleotides encoding a 1029 amino-acid protein, which had been expressed in Escherichia coli. Transferase activities in both recombinant and natural enzymes were similar.
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PMID:A novel beta-galactosidase capable of glycosyl transfer from Enterobacter agglomerans B1. 1733 32

The Hypocrea jecorina D-xylose reductase encoding gene xyl1 shows low basal transcript levels, and is induced by D-xylose, L-arabinose and L-arabinitol and, to a lesser extent, by lactose, D-galactose, galactitol and xylitol. The recombinantly expressed XYL1 catalyzes the NADPH-dependent reduction of the pentoses D-xylose and L-arabinose and the hexose D-galactose. Deletion of xyl1 slightly reduces growth on all carbon sources, but a significant decrease is found on D-xylose, L-arabinose and D-galactose. Similar to pentose degradation, XYL1 reduces D-galactose to galactitol in a recently identified second D-galactose pathway. Strains impaired in both D-galactose pathways are almost unable to grow on D-galactose. Deltaxyl1 strains show reduced growth on lactose and are impaired in beta-galactosidase expression and induction of the major cellobiohydrolase gene cbh1. A strain deleted in the cellulase regulator XYR1 is even more severely impaired in growth and beta-galactosidase expression on lactose, and does not produce any cbh1 transcript at all. In this strain, only a low basal level of xyl1 transcription is found on lactose. Galactitol, but not D-galactose is able to induce xyl1 transcription in a XYR1-independent manner. Our results show that the role of the H. jecorina XYL1 is not restricted to D-xylose catabolism and demonstrates its importance for induction of cellulases and beta-galactosidases.
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PMID:The D-xylose reductase of Hypocrea jecorina is the major aldose reductase in pentose and D-galactose catabolism and necessary for beta-galactosidase and cellulase induction by lactose. 1792 46

An integrated metabolic model for the production of acetate by Escherichia coli growing on glucose under aerobic conditions was presented previously (Ko et al., 1993). The resulting model equations can be used to explain phenomena often observed with industrial fermentations, i.e., increased acetate production which follows from high glucose uptake rate, a low dissolved oxygen concentration, a high specific growth rate, or a combination of these conditions. However, several questions still need to be addressed. First, cell composition is growth rate and media dependent. Second, the macromolecular composition varied between E. coli strains. And finally, a model that represents the carbon fluxes between the Embden-Meyerhof-Parnas (EMP) and the hexose monophosphate (HMP) pathways when cells are subject to internal and/or external stresses is still not well defined. In the present work, we have made an effort to account for these effects, and the resulting model equations show good agreement for wild-type and recombinant E. coli experimental data for the acetate concentration, the onset of acetate secretion, and cell yield based on glucose. These results are useful for optimizing aerobic E. coli fermentation processes. More specifically, we have determined the EMP pathway carbon flux profiles required by the integrated metabolic model for an accurate fit of the acetic acid profile data from a wild-type E. coli strain ML308. These EMP carbon flux profiles were correlated with a dimensionless measurement of biomass and then used to predict the acetic acid profiles for E. coli strain F-122 expressing human immunodeficiency virus-(HIV(528)) beta-galactosidase fusion protein. The effect of different macromolecular compositions and growth rates between these two E. coli strains required a constant scaling factor for improved quantitative predictions.
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PMID:A metabolic model of cellular energetics and carbon flux during aerobic Escherichia coli fermentation. 1861 77

A novel beta-galactosidase of 120 kDa (BgaBM) from Bacillus megaterium 2-37-4-1 was purified, and its gene (bgaBM) was analyzed and expressed. It displayed wide acceptor specificity for transglycosylation with a series of acceptors, including pentose, hexose, hydroxyl, and alkyl alcohol using o-nitrophenyl-beta-D-galactoside (ONPG) as a donor. BgaBM preferentially hydrolyzed ONPG in all tested substrates and showed maximum activity at pH 7.5-8.0 and 55 degrees C. It was stable at pH 6.0-9.0 below 40 degrees C. The K(m) and V(max) values for ONPG and lactose were 9.5 mM, 16.6 mM/min and 12.6 mM, 54.4 mM/min, respectively. The nucleotide sequence of the bgaBM gene consists of an ORF of 3,105 bp corresponding to 118 kDa protein, which indicates that BgaBM is a modular enzyme in the glycosyl hydrolase family 2, including conserved sugar-binding domain, acid-base catalyst, and immunoglobulin-like beta-sandwich domain. The possible acid/base and nucleophile sites of BgaBM were estimated to be E481 and E547, respectively. Furthermore, expression of the bgaBM gene in Escherichia coli and purification of the recombinant enzyme were performed. The recombinant enzyme showed similar biochemical characteristics to natural enzyme.
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PMID:Purification and characterization of a novel beta-galactosidase with transglycosylation activity from Bacillus megaterium 2-37-4-1. 1868 99

We report the isolation of a novel bacterium, strain C1(T), from the midgut of the tsetse fly Glossina palpalis gambiensis, one of the vector insects responsible for transmission of the trypanosomes that cause sleeping sickness in sub-Saharan African countries. Strain C1(T) is a motile, facultatively anaerobic, rod-like bacterium (0.8-1.0 microm in diameter; 2-6 microm long) that grows as single cells or in chains. Optimum growth occurred at 25-35 degrees C, at pH 6.7-8.4 and in medium containing 5-20 g NaCl l(-1). The bacterium hydrolysed urea and used L-lysine, L-ornithine, citrate, pyruvate, D-glucose, D-mannitol, inositol, D-sorbitol, melibiose, amygdalin, L-arabinose, arbutin, aesculin, D-fructose, D-galactose, glycerol, maltose, D-mannose, raffinose, trehalose and d-xylose; it produced acetoin, reduced nitrate to nitrite and was positive for beta-galactosidase and catalase. The DNA G+C content was 53.6 mol%. It was related phylogenetically to members of the genus Serratia, family Enterobacteriaceae, the type strain of Serratia fonticola being its closest relative (99 % similarity between 16S rRNA gene sequences). However, DNA-DNA relatedness between strain C1(T) and S. fonticola DSM 4576(T) was only 37.15 %. Therefore, on the basis of morphological, nutritional, physiological and fatty acid analysis and genetic criteria, strain C1(T) is proposed to be assigned to a novel Serratia species, Serratia glossinae sp. nov. (type strain C1(T) =DSM 22080(T) =CCUG 57457(T)).
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PMID:Serratia glossinae sp. nov., isolated from the midgut of the tsetse fly Glossina palpalis gambiensis. 1966 82

Beta-(1-->4)-thiodisaccharides formed by a pentopyranose unit as reducing or non reducing end have been synthesized using a sugar enone derived from a hexose or pentose as Michael acceptor of a 1-thiopentopyranose or 1-thiohexopyranose derivatives. Thus, 2-propyl per-O-acetyl-3-deoxy-4-S-(beta-D-Xylp)-4-thiohexopyranosid-2-ulose (3) and benzyl per-O-acetyl-3-deoxy-4-S-(beta-D-Galp)-4-thiopentopyranosid-2-ulose (11) were obtained in almost quantitative yields. The carbonyl function of these uloses was reduced with NaBH(4) or K-Selectride, and the stereochemical course of the reduction was highly dependent on the reaction temperature, reducing agent and solvent. Unexpectedly, reduction of 3 with NaBH(4)-THF at 0 degrees C gave a 3-deoxy-4-S-(beta-D-Xylp)-4-thio-alpha-D-ribo-hexopyranoside derivative (6) as major product (74% yield), with isomerization of the sulfur-substituted C-4 stereocenter of the pyranone. Reduction of 11 gave always as major product the benzyl 3-deoxy-4-S-(Galp)-4-thio-beta-D-threo-pentopyranoside derivative 14, which was the only product isolated (80% yield) in the reduction with K-Selectride in THF at -78 degrees C. Deprotection of 14 and its epimer at C-2 (13) afforded, respectively the free thiodisaccharides 19 and 18. They displayed strong inhibitory activity against the beta-galactosidase from Escherichia coli. Thus, compound 18 proved to be a non-competitive inhibitor of the enzyme (K(i)=0.80 mM), whereas 19 was a mixed-type inhibitor (K(i)=32 microM).
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PMID:Synthesis of pentopyranosyl-containing thiodisaccharides. Inhibitory activity against beta-glycosidases. 1967 8

A practical purification method for a non-digestible disaccharide, epilactose (4-O-beta-galactosyl-D-mannose), was established. Epilactose was synthesized from lactose with cellobiose 2-epimerase and purified by the following procedure: (i) removal of lactose by crystallization, (ii) hydrolysis of lactose by beta-galactosidase, (iii) digestion of monosaccharides by yeast, and (iv) column chromatography with Na-form cation exchange resin. Epilactose of 91.1% purity was recovered at 42.5% yield.
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PMID:Practical preparation of epilactose produced with cellobiose 2-epimerase from Ruminococcus albus NE1. 2069 53


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