Solubilization and Selected Properties of Crambe Seed Thioglucosidase (Thioglucoside Glucohydrolase, EC 3.2.3.1)

Abstract

Ultrasonic treatment releases thioglucoside glucohydrolase (thioglucosidase) from insoluble particles of Crambe abyssinica seed meal. The crude enzyme is optimally activated by 10−2 M ascorbate, requires a reducing agent for stability, and is inhibited by 10−3 M p-chloromercuribenzenesulfonate.Chromatography of a meal extract on cross-linked dextran separates two enzyme fractions. About 80% of the activity elutes at an apparent molecular weight of 110 000; the remainder elutes at the void volume. Both crude soluble enzyme and the fractions from the dextran column produce goitrin from epi-progoitrin, but in the presence of ferrous ion the chief aglucon product becomes 1-cyano-2-hydroxy-3-butene. The Michaelis constant (of the major peak) at pH 5 is 0.004 M. Ferrous ion produces substrate inhibition at high epi-progoitrin levels. Sequential fractionation of meal extract by ammonium sulfate precipitation and by chromatography on cross-linked dextran effects an 80-fold purification.