NaF inhibition of phosphorylation and dephosphorylation involved in α-methyl-D glucoside transport in E. coli K 12. A pH dependant phenomenon sensitive to uncoupling agents

Abstract

Summary In a previous article we reported the observation that during the phosphorylative uptake of α-methyl glucoside (αmg) in Escherichia coli two inhibitors, an uncoupler and sodium fluoride are required to inhibit the synthesis of phosphoenol pyruvate and the hydrolysis of the sugar phosphate formed. This observation prompted the search for a sugar phosphatase with peculiar regulatory properties. Phosphatase(s) capable to hydrolyse αmg6P were found to be inhibited by fluoride alone, and did not exhibit obvious regulatory properties. Fluoride inhibition exhibited a sharp pH dependence, being strong at acidic and nil at alkaline pH. The in vivo processes of phosphorylation and dephosphorylation were found to be inhibited by fluoride alone but the pH dependence curve of these inhibitions was shifted by 0.6–0.7 pH units toward acidic pH. Addition of uncoupling agents restored the pH dependence observed in vitro. It was concluded, that intracellular pH of glycerol grown E. coli in aerobiosis is about 0.7 pH units more alkaline than the surrounding medium, but uncoupling agents cause equilibration of hydrogen ion concentration between medium and cytoplasm.