Studies on the Myrosinase in Mustard Seed

Part II. On the Activation Mode of the Myrosinase by L-Ascorbic Acid

Abstract

The mechanism of activation of plant myrosinase by ascorbic acid was studied. The oxidation-reduction reaction of ascorbic acid had nothing to do with the reaction by the activated myrosinase. Presence of firmely bound ascorbic acid in the enzyme protein was doubtful from the result of incubation with ascorbate oxidase. Presence of the effector site for ascorbic acid was presumed by the kinetic measurement and the instabilization by ascorbic acid in heating. But the effector site and the substrate site could not be distinguishable experimentally. The affinity of ascorbic acid to the myrosinase was not influenced by the substrate. The differences of the activation mechanism of the myrosinase by ascorbic acid and the allosteric enzyme were discussed.