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 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

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

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


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