Functional characteristics of pyruvate transport in Phycomyces blakesleeanus

A saturable and accumulative transport system for pyruvate has been detecte d in Phycomyces blakesleeanus NRRL 1555(-) mycelium, It was strongly inhibi ted by alpha-cyano-4-hydroxycinnamate, L-Lactate and acetate were competiti ve inhibitors of pyruvate transport. The initial pyruvate uptake velocity a nd accumulation ratio was dependent on the external pH, The V-max of transp ort greatly decreased with increasing pH, whereas the affinity of the carri er for pyruvate was not affected, The pyruvate transport system mediated it s homologous exchange, which was essentially pH independent, and efflux, wh ich increased with increasing external pH, The uptake of pyruvate was energ y dependent and was strongly inhibited by inhibitors of oxidative phosphory lation and of the formation of proton gradients. Glucose counteracted the i nhibitory effect of the pyruvate transport produced by inhibitors of mitoch ondrial ATP synthesis. Our results are consistent with a pyruvate/proton co transport in P, blakesleeanus probably driven by an electrochemical gradien t of H+ generated by a plasma membrane H+-ATPase, (C) 1998 Academic Press.