Comparative biochemical studies on .ALPHA.-glucosidases. IX. Substrate specificity of flint corn .ALPHA.-glucosidase.

The substrate specificity of flint corn α-glucosidase was investigated. The enzyme was active especially on nigerose, phenyl-α-maltoside and malto-oligosaccharides. The action on isomalto-oligosaccharides was very weak. The α-glucans, such as amylopectin, β-limit dextrin, glycogen and amylose besides soluble starch, also were hydrolyzed, though no activity on dextran was observed. The ratio of hydrolysis rate for maltose, nigerose, phenyl-α-maltoside, maltotriose, maltotetraose and maltopentaose was estimated to be 100:105:110:97:100:90 in this order. The extrapolated Km values for maltose, nigerose, phenyl-α-maltoside, maltotriose, malto-tetraose and maltopentaose were 1.25mM, 1.43maM, 1.00mM, 0.71mM, 0.60mM and 1.25mM, respectively. The enzyme is considered to be essentially an acid α-glucosidase with a preferential activity on malto-oligosaccharides to α-glucans.