ORIGIN AND DISTRIBUTION OF α-AMYLASE IN MALT

Abstract

Estimation of the α-amylase in various parts of germinating, dehusked whole barley and in sections of the grain cultured in vitro, shows that in malt some 7% of the α-amylase is located in the embryo while, of the remaining 93% in the endosperm, about 6.5% originated in the embryo and 86.5% in the aleurone layer. Various parts of the aleurone layer responded equally well to gibberellic acid, in modifying the adjacent endosperm. In presence of gibberellic acid, isolated pieces of aleurone layer increased their respiration slightly and released α-amylase along with other enzymes, without supply of an external source of nitrogen. On the other hand, the production of α-amylase by barley embryos was best supported by a mixture of amino acids in the form of a commercial casein hydrolysate. Under some circumstances sugars suppressed enzyme production, but gibberellic acid increased α-amylase production when the culture medium contained casein hydrolysate. Various metabolic poisons and amino acid analogues decreased the levels of α-amylase found while depressing the amount of radio-activity incorporated from labelled amino acids, suggesting that de novo protein synthesis is involved in the production of α-amylase by the embryo as in the earlier findings with aleurone layer. Acetate decreased acrospire growth though it supported α-amylase production, suggesting that this substance might be used as a growth regulator in malting.