Pyruvate catabolism during transient state conditions in chemostat cultures of Enterococcus faecalis NCTC 775: importance of internal pyruvate concentrations and NADH/NAD+ ratios

Enterococcus faecalis was grown in glucose-limited chemostat cultures under aerobic and anaerobic conditions to study the regulation of pyruvate catabolism. Switching from aeorbic to anaerobic growth resulted in a rapid increase of the NADH/NAD+ ratio with a concomitant inhibition of the pyruvate dehydrogenase complex (PDC). In contrast, switching from anaerobic to aerobic growth increased both PDC activity and NADH/NAD+ ratio. A pyruvate pulse also resulted in catabolic fluxes. Therefore, both NADH/NAD+ ratio and pyruvate concentration are important in regulating PDC.