Pyruvate uptake induced by a pH jump in mesophyll chloroplasts of maize and sorghum, NADP-malic enzyme type C4 species.

A sudden pH decrease (pH jump) of the medium enhanced pyruvate uptake in the dark in mesophyll chloroplasts (MCp) of Zea mays and Sorghum bicolor, NADP-malic enzyme type C4 plants, while it was reported that a Na+ jump enhanced pyruvate uptake in MCp of P. miliaceum, a NAD-malic enzyme type [(1987) FEBS Lett. 219, 347]. The enhancement effect of the pH jump decayed completely in 5 min and the decay was accelerated by proton gradient-collapsing reagents. The results suggest that active pyruvate uptake into MCp of NADP-malic enzyme type C4 species is primarily driven by the proton gradient across the envelope.