OCCURRENCE AND INFLUENCE OF LIGHT ON THE RELATIVE PROPORTIONS OF 2 GLUTAMINE SYTHETASES IN RICE LEAVES

Two glutamine synthetases (GS1 and GS2) were identified in green rice leaves by chromatography on a DEAE-cellulose column. The contribution of GS2 to the total activity was high compared to GS1. When an extract from dark-grown leaves was chromatographed, two peaks of enzymatic activity were also detected but in this case GS1 was predominant. During the greening of etiolated leaves GS1 decreased while GS2 increased, and after a light exposure of 48 h the typical pattern of green leaves was obtained. When GS1 and GS2 were rechromatographed no interconversion occurred. The Km values for glutamate and the heat stabilities of the two enzymes were shown to be different. © 1979.