Acta Univ Latv (2005) 691: 71–81

Intracellular redox state regulates the resistance of Zymomonas mobilis alcohol dehydrogenase II to cyanide and oxygen

Abstract

The variable sensitivity of Zymomonas mobilis iron-containing alcohol dehydrogenase isoenzyme (ADH II) to cyanide and oxygen was studied. The cyanide-sensitivity of ADH II was highest in cells grown under conditions of vigorous aeration, in which intracellular NADH concentration was low. Anaerobically grown bacteria, as well as those cultivated aerobically in the presence of cyanide, maintained a higher intracellular NADH pool along with a more cyanide-resistant ADH II. In aerobically grown permeabilized cells, cyanide caused gradual inhibition of ADH II, which was largely prevented by externally added NADH, and, to lesser extent, by NAD. It was demonstrated that cyanide acted as a competitive inhibitor of ADH II, competing with nicotinamide nucleotides. NADH increased both the cyanide resistance and oxygen resistance of ADH II.