Required for plastidial pyruvate kinase activity. ATP + pyruvate = ADP + H(+) + phosphoenolpyruvate Optimum pH is 7.8-8.0. Carbohydrate degradation; glycolysis; pyruvate from D-glyceraldehyde 3-phosphate: step 5/5. Oligomer of alpha and beta subunits. Expressed at low levels in roots, leaves, inflorescences, siliques, pollen, seeds and flowers. Belongs to the pyruvate kinase family.