Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: KEGG:D03345 (beta-Galactosidase)
 434 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An intracellular beta-glycoside hydrolase with beta-glucosidase and beta-galactosidase activity, designated beta-glucosidase BGL1, was isolated to apparent homogeneity from the thermophilic ascomycete Talaromyces thermophilus CBS 236.58. The monomeric enzyme has a molecular mass of 50 kDa (SDS-PAGE) and an isoelectric point of 4.5-4.6. The enzyme is active with both glucosides such as cellobiose and galactosides including lactose; based on the catalytic efficiencies determined glucosides are the preferred substrates. beta-Galactosidase activity of BGL1 is activated by various mono and divalent cations including Na+, K+ and Mg2+, and it is moderately inhibited by its reaction products glucose and galactose. Its pH optimum for the hydrolysis of galactosides is in the range of 5.5-6.0, and its optimum temperature was found to be 50 degrees C (15 min assay). In addition to its hydrolytic activity, BGL1 shows a significant transferase activity which results in the formation of galacto-oligosaccharides. These have recently attracted interest because of possible applications in food industry. The highest yields of oligosaccharides was approximately 20% when using 38 gl(-1) lactose as the starting material.
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PMID:Purification and characterisation of an intracellular enzyme with beta-glucosidase and beta-galactosidase activity from the thermophilic fungus Talaromyces thermophilus CBS 236.58. 1644 2

beta-Galactosidase from the fungus Talaromyces thermophilus CBS 236.58 was immobilized by covalent attachment onto the insoluble carrier Eupergit C with a high binding efficiency of 95%. Immobilization increased both activity and stability at higher pH values and temperature when compared with the free enzyme. Especially the effect of immobilization on thermostability is notable. This is expressed by the half-lifetime of the activity at 50 degrees C, which was determined to be 8 and 27 h for the free and immobilized enzymes, respectively. Although immobilization did not significantly change kinetic parameters for the substrate lactose, a considerable decrease in the maximum reaction velocity V(max) was observed for the artificial substrate o-nitrophenyl-beta-D-galactopyranoside (oNPG). The hydrolysis of both oNPG and lactose is competitively inhibited by the end products glucose and galactose. However, this inhibition is only very moderate as judged from kinetic analysis with glucose exerting a more pronounced inhibitory effect. It was evident from bioconversion experiments with 20% lactose as substrate, that the immobilized enzyme showed a strong transgalactosylation reaction, resulting in the formation of galactooligosaccharides (GalOS). The maximum yield of GalOS of 34% was obtained when the degree of lactose conversion was roughly 80%. Hence, this immobilized enzyme can be useful both for the cleavage of lactose at elevated temperatures, and the formation of GalOS, prebiotic sugars that have a number of interesting properties for food applications.
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PMID:Lactose hydrolysis and formation of galactooligosaccharides by a novel immobilized beta-galactosidase from the thermophilic fungus Talaromyces thermophilus. 1691 41