TRANSPORT OF MALATE AND CHLORIDE INTO BARLEY MESOPHYLL VACUOLES - DIFFERENT CARRIERS ARE INVOLVED

Transport of malate and chloride across the tonoplast of barley mesophyll vacuoles has been compared. Whereas malate inhibited chloride uptake, 1,2,3-benzenetricarboxylic acid, a potent inhibitor of malate uptake which is assumed not to cross the tonoplast, was ineffective. In contrast to chloride uptake, malate uptake was inactivated by pyridoxal phosphate and phenylglyoxal. The malate transport system could be protected against pyridoxal phosphate when a substrate such as 1,2,3-benzenetricarboxylic acid was present in the preincubation medium. It is concluded that the transfer of malate and chloride across the tonoplast is mediated by different systems. © 1990.