The localization of nitrite reductase, glutamate synthase and malate metabolism enzymes in Pisum arvense L. roots

Abstract

Centrifugation of a homogenate made from Pisum arvense L. roots in a sucrose density gradient enabled the separation of the plastid fraction from mitochondria and microsomes. The presence of nitrite reductase and glutamate synthase was demonstrated in the plastids. Malic enzyme activity was not linked with any organelle fraction and was found only in the cytosol. High malate dehydrogenase activity was found in the mitochondria fraction, although its activity was also determined in plastids. The results suggest that malic acid metabolism in plastids may be the source of reduced pyridine nucleotides for reactions catalysed by nitrite reductase and glutamate synthase.

Keywords

• roots
• nitrogen metabolism enzymes
• malate dehydrogenase