Study on bacterial myrosidase. II. Purification and General characteristics of bacterial myrosinase produced by Enterobacter cloacae.

Myrosinase in cell-free extract of Enterobacter cloacae, no. 506, was purified about 1, 000 fold by precipitation with ammonium sulfate, chromatography on CM-Sephadex and gelfiltration on Sephadex G-200 and Sephadex G-100. The enzyme was shown to be homogeneous by chromatography and by ultracentrifuge. Molecular weight obtained by gelfiltration was 61, 000 and the sedimentation coefficient was 4.5S. Maximum activity occurred at pH 6.8. The enzyme was stable in a pH range of 5.0 to 7.0 at temperature below 40°C and for 24 hr. Copper(I) and (II), mercury (II) and ferrous(II) ions strongly inhibited the activity. Sulfhydryl reagents had little effect but EDTA was a strong inhibitor. In contrast to plant myrosinase, this enzyme was inhibited by L-ascorbic acid. Many glucosides and sugars inhibited the enzyme. The relation between bacterial myrosinase and β-glucosidase is discussed in comparison to plant and fungous myrosinases. Some comparative properties of bacterial, fungous and plant myrosinases are discussed.