The myrosinase from Wasabi (Wasabia japonica) is effectively extracted by sonication. The enzyme is purified about 100-fold by gel-filtration on Sephacryl S-200, Sepharose 6B and ion-exchange chromatography on DEAE-Sephadex. The enzyme is active only when L-ascorbic acid is added to the reaction mixture. General reducing reagents (2-mercaptoethanol and dithiothreitol) do not activate the enzyme. Sulfhydryl and amino group discriminating reagents strongly inhibit the enzyme activity. These results suggest that amino groups and sulfhydryl groups constitute the active sites of the enzyme.Molecular weight as determined by gel-filtration is 580,000, and the enzyme has about 12 subunits as assessed by SDS-polyacrylamide electrophoresis. Km value for sinigrin is. 4.7 × 10−4m.Comparative findings on some properties of yellow mustard, microbial and Wasabi myrosinases are reported.