Kinetics and inhibitory action of hydrolysis of o-nitrophenyl-β-D-galactopyranoside catalyzed by immobilized β-D-galactosidase on macroporous resin

Department of Chemistry, Lanzhou University, Lanzhou 730000, P. R. China

Manuscript received 21 March 1997, revised 27 July 1998, accepted 4 August 1998

β-Galactosidase (β-D-galactoside galactosyl hydrolase EC 3.2.1.23) purified from Cicer arietinum has been immobilized on modified and actived macroporous resin D₂₀₂(dimethylethoxymethylaminopolyphenylethylene anion-exchange resin) with high enzyme activity and high activity yield by means of adsorption of ions and crosslinked reaction. Catalytic kinetic results of immobilized β-galactosidase show that enzyme activity attains its maximum at 55^°, pH 6.0, and the operational pH range and its thermostability range are increased compared to those of free enzyme. In addition, kinetic parameters K_m, V_rn and E. of the immobilized enzyme are slightly different from those of free enzyme. Raffinose, lactose and D-galactose are all reversible inhibitors for this enzyme. Their inhibitory kinetics are also studied.