CHARACTERIZATION OF BETA-GALACTOSIDASE FROM KLUYVEROMYCES-LACTIS

The properties and kinetic studies of a lactase from Kluyveromyces lactis are presented. The enzyme was subjected to both normal and denaturing electrophoresis and shown to be a dimer of M(r) of 200000, composed of two identical subunits. The lactase is a glycoprotein with 45% (w/w) carbohydrate. The Michaelis-Menten constants were determined with respect to o-nitrophenyl beta-D-galactopyranoside and lactose and were 1.7 and 17.3 mM, respectively. Galactose and glucose were competitive and non-competitive Inhibitors, respectively. A mathematical description of the kinetic data from a total lactose hydrolysis is proposed. High enzyme stability required K+ and Mg2+, and the activity was rapidly lost in deionized water.