Functional Characteristics of Pyruvate Transport inPhycomyces blakesleeanus

Abstract

Jesús A. Marcos, Dolores de Arriaga, Félix Busto, and Joaquı́n Soler11997. Functional Characteristics of Pyruvate Transport inPhycomyces blakesleeanus. Fungal Genetics Biology25, 204-215. A saturable and accumulative transport system for pyruvate has been detected inPhycomyces blakesleeanusNRRL 1555(−) mycelium. It was strongly inhibited by α-cyano-4-hydroxycinnamate.l-Lactate and acetate were competitive inhibitors of pyruvate transport. The initial pyruvate uptake velocity and accumulation ratio was dependent on the external pH. TheVmaxof transport greatly decreased with increasing pH, whereas the affinity of the carrier for pyruvate was not affected. The pyruvate transport system mediated its homologous exchange, which was essentially pH independent, and efflux, which increased with increasing external pH. The uptake of pyruvate was energy dependent and was strongly inhibited by inhibitors of oxidative phosphorylation and of the formation of proton gradients. Glucose counteracted the inhibitory effect of the pyruvate transport produced by inhibitors of mitochondrial ATP synthesis. Our results are consistent with a pyruvate/proton cotransport inP. blakesleeanusprobably driven by an electrochemical gradient of H+generated by a plasma membrane H+-ATPase.