Enzyme Activation in Wheat Grains in Relation to Water Content. Glutamic Acid—Alanine Transaminase, and Glutamic Acid Decarboxylase.

Abstract

Enzymatic decarboxylation and transamination of glutamic acid were studied in wheat grains and excised wheat embryos by chromatographic and manometric techniques, in relation to water content. Moisture levels as low as 18% activate both enzyme systems, whose activity increases rapidly with moisture content up to that required for germination of the grain. Transamination of [alpha]-ketoglutarate with alanine occurred at moisture levels as low as 15%. At higher levels, transamination is followed by rapid decarboxylation of glutamate. Glutamic acid decarboxylase is located almost entirely in the embryo. In the intact grains,, other metabolic reactions overcome the decarboxylation of glutamate at moisture levels higher than 18%, resulting in a net production of glutamate. Significance of these results is discussed.