Nitrate Reduction by a Dicarboxylate Shuttle in a Reconstituted System from Spinach Leaves

Abstract

A reconstituted system of supernatant and mitochondria from spinach leaves reduced NO3- in the presence of NAD+. A faster rate (2-6 times) of NO3- reduction was obtained when oxaloacetate (OAA) and glycine were present. The reduction of NO3- in the presence of OAA and glycine was sensitive to inhibition by n-butyl malonate, suggesting that the dicarboxylate exchange carrier was involved in the transport of malate out of the mitochondria. The capacity of the dicarboxylate shuttle to reduce NO,- was 63 % that of the in vitvo nitrate reductase activity in the supernatant