Metabolism of phosphoenolpyruvate in the C4 cycle during photosynthesis in the phosphoenolpyruvate-carboxykinase C4 grass Spartina anglica Hubb.

The aim of this work was to investigate the fate of phosphoenolpyruvate (PEP) produced by decarboxylation of oxaloacetate during photosynthesis in the bundle sheaths of leaves of the PEP-carboxykinase C4 grass Spartina anglica Hubb. Mesophyll protoplasts and bundle sheath cells were separated enzymically and used to investigate activities and distributions of putative enzymes of the C4 cycle and the photosynthetic carbon metabolism of bundle sheath cells. The results indicate that neither conversion of PEP to pyruvate nor its conversion to 3-phosphoglycerate can account for all of the carbon flux through the C4 cycle during photosynthesis. It is likely, therefore, either that PEP moves directly from bundle sheath to mesophyll or that more than one pathway of regeneration of PEP is involved in the C4 cycle in this plant.