Sequential changes in amylase isozymes during grain maturation in barley

Abstract

Changes in amylase isozyme patterns on polyacrylamide gels were followed during maturation in grains of Deba Abed barley. Early stage seeds contained a single, high-mobility enzyme (Band A) which had an estimated molecular weight of 4.2×10⁴ and a high activity with β-limit dextrin as a substrate. It was shown, by dissection, that Band A was confined to the aleurone layer and probably represented the initial product of amylase synthesis. This form was succeeded, in mid-course, by a less mobile form (Band B), a β-amylase with a molecular weight of approximately 1.3×10⁵. Late-dough stage grains contained a complex of low-mobility β-amylase bands which were shown, by papain digestion, to be protein-bound forms of Band B. The changes are discussed on the basis of a unified series consisting of elaborated forms of the initial Band A type of activity.