Isolation and characterization of oxaloacetate decarboxylase of Salmonella typhimurium, a sodium ion pump

Abstract

Anaerobic growth of Salmonella typhimurium on citrate is Na+-dependent and requires induction of the necessary enzymes during a 20-40 h lag phase. The citrate fermentation pathway involves citrate lyase and oxaloacetate decarboxylase. The decarboxylase is a membrane-bound, Na+-activated, biotin-containing enzyme that functions as a Na+ pump. Oxaloacetate decarboxylase was isolated by affinity chromatography of a Triton X-100 extract of the bacterial membranes on avidin-Sepharose. The enzyme consists of three subunits alpha, beta, gamma, with apparent molecular weights of 63,800, 34,500 and 10,600. The alpha-chain contains a covalently attached biotin group and binds to antibodies raised against the alpha-subunit of oxaloacetate decarboxylase from Klebsiella pneumoniae. The Na+ transport function was reconstituted by incorporation of the purified enzyme into proteoliposomes.