Cereal Chem 40:220 - 230  |  VIEW ARTICLE

Glutamic-Aspartic Transaminase in the Germinating Barley Embryo.

W. C. Burger. Copyright 1963 by the American Association of Cereal Chemists, Inc. 

Selected barley varieties from irrigated land at Aberdeen, Idaho, were studied for possible relationships between (a) germination rate and embryo glutamic-aspartic transaminase (GAT) activity; (b) GAT activity and kernel nitrogen content; and (c) germination rate and kernel nitrogen content. Six barley varieties known to differ in their germination rates revealed no consistent relationships between GAT and germination rate. Two-rowed varieties were consistently high in GAT and germination rate. GAT increases of 36 to 49% during the first 24 hours were exhibited by these six varieties, while their embryo proteins changed by -3 to 8%. This fact plus a decreased response of the embryo homogenates to added pyridoxamine-5-phosphate as germination progressed suggests that the early increases in GAT result from activation of existing apoenzyme by endogenous coenzyme rather than via apoenzyme synthesis or the slow hydration of existing holoenzyme. The nitrogen contents of isogenic two-rowed and six-rowed barleys were varied by growing at different spacing intervals. These samples revealed only inconsistent increases in GAT content with increased nitrogen content. The samples with the higher nitrogen contents tended to germinate more slowly.