AMYLASES SYNTHESIS IN SCUTELLUM AND ALEURONE LAYER OF MAIZE SEEDS

The endosperm of germinating maize seeds contains four isozymes of alp ha-amylases (alpha-amylase-1 to -4) and one isozyme of beta-amylase. T he alpha-amylases were purified by affinity chromatography on amylose and separated by DEAE-cellulose chromatography, into two groups, namel y alpha-amylases-1,2 and alpha-amylases-3,4; and beta-amylase was puri fied by precipitation as a glycogen-enzyme complex. The molecular weig ht of alpha-amylases-1 and -2 was 46 kD, alpha-amylases-3 was 44.5 kD and of alpha-amylases-4 was 47.5 kD. The molecular weight of beta-amyl ase was 56 kD. During seed germination increase in amylolytic activity in endosperm was mainly contributed by secretion of alpha-amylases fr om adjoining aleurone layer and scutellum. The synthesis and secretion of alpha-amylases was first initiated in the scutellum followed by al eurone layers. Exogenous Ca2+ stimulated synthesis of alpha-amylases i n both eleurone layer and scutellum. In contrast, though scutellum and aleurone layer synthesized beta-amylase but it was not secreted to th e medium. These results suggest that during the early germination peri od, alpha-amylases secreted from scutellum mobilizes starch. (C) 1998 Elsevier Science Ltd. All rights reserved.