Amylases synthesis in scutellum and aleurone layer of maize seeds

Abstract

The endosperm of germinating maize seeds contains four isozymes of α- amylases (α-amylase-1 to -4) and one isozyme of β-amylase. The α-amylases were purified by affinity chromatography on amylose and separated by DEAE- cellulose chromatography, into two groups, namely α-amylases-1,2 and α- amylases-3,4; and β-amylase was purified by precipitation as a glycogen- enzyme complex. The molecular weight of α-amylases-1 and -2 was 46 kD, α- amylases-3 was 44.5 kD and of α-amylases-4 was 47.5 kD. The molecular weight of β-amylase was 56 kD. During seed germination increase in amylolytic activity in endosperm was mainly contributed by secretion of α-amylases from adjoining aleurone layer and scutellum. The synthesis and secretion of α- amylases was first initiated in the scutellum followed by aleurone layers. Exogenous Ca2+ stimulated synthesis of α-amylases in both eleurone layer and scutellum. In contrast, though scutellum and aleurone layer synthesized β-amylase but it was not secreted to the medium. These results suggest that during the early germination period, α-amylases secreted from scutellum mobilizes starch.