SEPARATION AND CHARACTERIZATION OF 3 BETA-GALACTOSIDASES FROM BACILLUS-CIRCULANS

Crude preparation of Bacillus circulans beta-galactosidase is known to have a good transglycolytic activity. Two isoforms of the enzyme have been described so far in the literature. Aiming at separating these t wo forms to assess their relative contribution to the regioselectivity of transglycosylation, we observed the presence of a third isoform ne ver described before. This paper deals with the isolation procedures o f the three enzymes and a re-consideration of their properties. The es timated molecular weight for the isoforms were 212kDa (I), 145kDa (II) and 86kDa (III), respectively. Kinetic parameters were determined tow ards the hydrolysis of o-nitrophenyl-beta-D-galactopyranoside (ONPG) a nd lactose. For ONPG the following values of K-m were found: 3.6, 5.0 and 3.3 mM for I, II and III, respectively, whereas for lactose the va lues were 3.7, 2.94 and 2.71 mM, respectively. (C) 1998 Elsevier Scien ce B.V.