CHANGES IN THE SIZE AND COMPOSITION OF INTRACELLULAR POOLS OF NONESTERIFIED COENZYME-A AND COENZYME-A THIOESTERS IN AEROBIC AND FACULTATIVELY ANAEROBIC-BACTERIA

Intracellular levels of three coenzyme A (CoA) molecular species, i.e. , nonesterified CoA (CoASH), acetyl-CoA, and malonyl-CoA, in a variety of aerobic and facultatively anaerobic bacteria were analyzed by the acyl-CoA cycling method developed by us, It was demonstrated that ther e was an intrinsic difference between aerobes and facultative anaerobe s in the changes in the size and composition of CoA pools, The CoA poo ls in the aerobic bacteria hardly changed and were significantly small er than those of the facultatively anaerobic bacteria, On the other ha nd, in the facultatively anaerobic bacteria, the size and composition of the CoA pool drastically changed within minutes in response to the carbon and energy source provided, Acetyl-CoA was the major component of the CoA pool in the facultative anaerobes grown on sufficient gluco se, although CoASH was dominant in the aerobes, Therefore, the acetyl- CoA/CoASH ratios in facultatively anaerobic bacteria were 10 times hig her than those in aerobic bacteria, In Escherichia coli K-12 cells, th e addition of reagents to inhibit the respiratory system led to a rapi d decrease in the amount of acetyl-CoA with a concomitant increase in the amount of CoASH, whereas the addition of cerulenin, a specific inh ibitor of fatty acid synthase, triggered the intracellular accumulatio n of malonyl-CoA. The acylation and deacylation of the three CoA molec ular species coordinated with the energy-yielding systems and the rest riction of the fatty acid-synthesizing system of cells, These data sug gest that neither the accumulation of acetyl-CoA nor that of malonyl-C oA exerts negative feedback on pyruvate dehydrogenase and acetyl-CoA c arboxylase, respectively.