Understanding the Role of Escherichia coli Hydrogenases and Formate Dehydrogenases in the F F -ATPase Activity during the Mixed Acid Fermentation of Mixture of Carbon Sources.

During fermentation Escherichia coli produces di-hydrogen (H ) via reversible membrane-bound [Ni-Fe]-hydrogenases (Hyd). This study describes the total and N,N'-dicyclohexylcarbodiimide (DCCD) inhibited ATPase activity and H production at various pHs in E. coli wild type and mutants encoding Hyd enzymes and formate dehydrogenases (FDH) on fermentation of glucose, glycerol, and formate. The highest total ATPase activity was detected at pH 7.5 in hyaB hybC selC (lacking large subunits of Hyd-1 and Hyd-2 and FDH, respectively) triple mutant. This ATPase activity was mainly due to the proton-translocating ATPase but in FDH mutant the DCCD inhibition was less compared to wild type. Potassium ions stimulated total ATPase activity at pH 5.5 ~50% and ~35% in wild type and hypF (lacking all Hyd enzymes) mutant, respectively. Moreover, K also stimulated DCCD inhibited ATPase activity ~1.7-fold-2-fold in strains where FDH was absent only at pH 5.5. DCCD inhibited H production only at pH 5.5 in all assays. Taken together it is suggested that at low pH, FDH, and Hyd enzymes are linked with the F F -ATPase for regulating and maintaining the cytoplasmatic pH and thus proton motive force generation. FDH and Hyd enzymes have impact on the F F -ATPase activity depending on external pH and potassium ions. © 2018 IUBMB Life, 70(10):1040-1047, 2018.