Hydrolysis of beta-galactosyl ester linkage by beta-galactosidases.
p-Hydroxybenzoyl beta-galactose (pHB-Gal) was synthesized chemically to examine the hydrolytic activity of beta-galactosyl ester linkage by beta-galactosidases. The enzyme from Penicillium multicolor hydrolyzed the substrate as fast as p-nitrophenyl beta-galactoside (pNP-Gal), a usual substrate with a beta-galactosidic linkage. The enzymes from Escherichia coli and Aspergillus oryzae hydrolyzed pHB-Gal with almost the same rates as pNP-Gal. The enzymes from Bacillus circulans, Saccharomyces fragilis, and bovine liver showed much lower activities. pH-activity profiles, inhibition analysis, and kinetic properties of the enzymic reaction on pHB-Gal suggested that beta-galactosidase had only one active site for hydrolysis of both galactosyl ester and galactoside. The Penicillium enzyme hydrolyzed pHB-Gal in the presence of H218O to liberate galactose containing 18O. This result suggests the degradation occurs between the anomeric carbon and an adjacent O atom in the ester linkage of pHB-Gal.
Kiso
T
T
Osaka Municipal Technical Research Institute, Japan. tkiso@omtri.city.osaka.jp
Nakano
H
H
Nakajima
H
H
Terai
T
T
Okamoto
K
K
Kitahata
S
S
D000818:Animals; D001236:Aspergillus oryzae / Q000201:enzymology; D001407:Bacillus / Q000201:enzymology; D002236:Carbohydrate Conformation; D002417:Cattle; D004926:Escherichia coli / Q000201:enzymology; D005690:Galactose / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008099:Liver / Q000201:enzymology; D010407:Penicillium / Q000201:enzymology; D013379:Substrate Specificity; D001616:beta-Galactosidase / Q000378:metabolism*
D001616:beta-Galactosidase; D005690:Galactose