Effect of N-Ethylmaleimide on the Starch-liquefying Enzyme from Soy-flour

Abstract

INFORMATION regarding soy-bean enzymes catalysing the breakdown of starch is contradictory or at best conjectural. The biological function of amylases in soy-beans is obscure as the beans contain very little-starch. The consensus of opinion seems to be that soy-bean seeds are a good source of β-amylase. While some workers1–3 feel that soy-beans contain no or only traces of α-amylase, Teller's investigations4 and evidence from the effects of soy-flour on starch-viscosity measurements5–7 point to the presence of a starch-liquefying enzyme in non-germinated soy-beans. Recently8, the presence of a starch-liquefying and of a starch-saccharifying enzyme in soy-flour was demonstrated by differential thermal inactivation. This communication deals with the effect of the SH-blocking reagent N-ethylmaleimide-(NEMI) on the starch-hydrolysing enzymes of soy-flour. It is known9 that none of the α-amylase so far investigated contains free sulphydryl groups essential for enzymatic: activity. β-Amylase purified and crystallized from soy-beans has been reported10 to contain —SH groups essential for enzymatic activity.