General Characteristics of the Intracellular Myrosinase from Aspergillus niger

Abstract

The enzymatic properties of intracellular myrosinase produced by Aspergillus niger AKU 3302 were investigated. Maximum activity occurred at pH 6.2, and the enzyme was stable in a pH range of 7.6 to 8.0 at 5°C for 24 hr. Optimum temperature was about 34°C. Enzyme activity was stimulated by copper (I), (II), manganese (II) and cobalt (II) and was inhibited by mercury (II) and stannous (II) ions. However, metal complexing agents and DFP had little effect, while PCMB was a strong inhibitor. In contrast to plant myrosinase, this enzyme was neither activated nor inhibited by L-ascorbic acid. Glucosides and δ-gluconolactone inhibited enzyme activity but sugars were ineffective. The Km value for sinigrin was 3.3×10^-3M and that for p-nitrophenyl β-glucoside was 1.5×10^-3M. The relation between fungous myrosinases and β-glucosidase is discussed in comparison to plant myrosinase.