Formation of C-4 dicarboxylic acids by intact spinach chloroplasts.

It is concluded from (14)C labelling kinetics as well as from enzyme analysis that formation of malate and aspartate from glycerate-3P via carboxylation of P-enolpyruvate occurs in isolated photosynthesizing spinach (Spinacia oleracea L.) chloroplasts. Carbon incorporation into both dicarboxylic acids was about 1% of the total CO2 fixation. Both acids are suggested to act as substrates for counter exchange for glutamate and α-ketoglutarate.