Regulation of Arginine Metabolism in Germinating Peanut ( Arachis hypogea L.) Seeds

Abstract

Summary Regulation of arginase (EC 3.5.3.1), ornithine ketoacid aminotransferase (EC 2.6.1.13), and ornithine carbamyltransferase (EC 2.1.3.3) was investigated by measuring the specific activities of these enzymes in the cotyledons and the embryo axis of germinating peanut ( Arachis hypogea L.) seeds grown under various conditions. It was observed that the activities of arginase and ornithine ketoacid aminotransferase of peanut cotyledons and embryo axis were reduced by auxins, ethrel, and ethylene chlorohydrin at early stages of germination. In the cotyledons, the activities of these enzymes returned to the control level as seedling growth progressed. However, in case of the embryo axis, the activities of these enzymes increased to more than the control levels. Exogenous polyamines increased the activities of these enzymes in the embryo axis and this encrease in the activities was prevented by cycloheximide. The activity of ornithine carbamyltransferase of the cotyledons and the embyo axis was not affected by any of these compounds. That the regulatory control on the embryo axis arginase and ornithine ketoacid aminotransferase was not influenced by the accompanying cotyledons, was demonstrated by cultivating the embryo axis in a synthetic medium.