J. Biochem, 1974, Vol. 76, No. 6 1155-1163
© 1974 Japanese Biochemical Society
research-article |
Purification of a ß-Galactosidase from Hog Small Intestine and Its Action on Glycoproteins and Glycopeptides1
Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Kyoto University Sakyo-ku, Kyoto, Kyoto 606
Of the ß-galactosidases [EC 3.2.1.23
[EC]
] extracted from hog small intestine, a ß-galactosidase capable of acting on glycoproteins was separated from other ß-galactosidases, i.e. lactase and hetero ß-galactosidase, and purified to a nearly homogeneous state. The purified preparation had specific activities of 3.00 and 3.64 units per mg protein towards lactose and o-nitrophenyl ß-galactoside, respectively, and was practically free from other important glycosidases including 
-galactosidase [EC 3.2.1.22
[EC]
].
The purified enzyme was rather unstable, losing all its activity after incubation at 37° for 24 hr, though it was stable indefinitely if frozen. Glycerol stabilized the enzyme significantly, 60% of the activity still remaining under the above conditions. In the presence of glycerol, however, the lactase activity and the activity towards glycoproteins were partially inhibited.
The purified enzyme was used to hydrolyze the galactosidic linkages in the carbohydrate chains of 1-acid glycoprotein (1-AGP) and ceruloplasmin of human plasma. The enzyme removed about 80% of the total galactose residues from sialic acid-free 1-AGP. It acted on glycopeptides more extensively, more than 90% of the total galactose residues being removed from sialic acid-free glycopeptides prepared from 1-AGP and ceruloplasmin. -Galactosidases obtained in the present study were not capable of releasing galactose from these glycopeptides or ß-galactosidasedigested glycopeptides.
1This study was supported in part by a grant from the Ministry of Education.