DIFFERENCES IN SENSITIVITY TO NADH OF PURIFIED PYRUVATE-DEHYDROGENASECOMPLEXES OF ENTEROCOCCUS-FAECALIS, LACTOCOCCUS-LACTIS, AZOTOBACTER-VINELANDII AND ESCHERICHIA-COLI - IMPLICATIONS FOR THEIR ACTIVITY IN-VIVO

The effect of NADH on the activity of the purified pyruvate dehydrogen ase complexes (PDHc) of Enterococcus (Ec.) faecalis, Lactococcus lacti s, Azotobacter vinelandii and Escherichia coli was determined in vitro . It was found that the PDHc of E. coli and L. lactis was active only at relatively low NADH/NAD ratios, whereas the PDHc of Ec. faecalis wa s inhibited only at high NADH/NAD ratios. The PDHc of Azotobacter vine landii showed an intermediate sensitivity. The organisms were grown in chemostat culture under conditions that led to different intracellula r NADH/NAD ratios and the PDHc activities in vivo could be calculated from the specific rates of product formation. Under anaerobic growth c onditions, only Ec. faecalis expressed PDHc activity in vivo. The acti vities in vivo of the complexes of the different organisms were in goo d agreement with their properties determined in vitro. The physiologic al consequences of these results are discussed.