Some regulatory properties of glutamine synthetase isoforms in a C4 plant: Pennisetum americanum (L.) Leeke

Abstract Some properties of cytosolic (GS 1) and chloroplastic (GS 2) glutamine synthetases were studied and compared in a C 4 ( Pennisetum americanum ) and a C 3 plant ( Oryza sativa L.). Although similar kinetic and regulatory properties were found for the enzymes of each plant type the relative proportions of GS 1 and GS 2 were markedly different. The possible physiological role of each isoform is discussed in relation to their regulatory properties and their levels of activity in the cytosol and chloroplast during the light/dark transition-period.