CHANGES IN SIZE OF INTRACELLULAR POOLS OF COENZYME-A AND ITS THIOESTERS IN ESCHERICHIA-COLI K-12 CELLS TO VARIOUS CARBON-SOURCES AND STRESSES

Intracellular pools of three CoA molecular species of coenzyme A, CoAS H, acetyl-CoA, and malonyl-CoA, in Escherichia coli K-12 cells were st udied by acyl-CoA cycling method in replacement culture. The sizes and compositions of CoA pools starved for a carbon source changed within minutes after the addition of one of various carbon sources. A large a cetyl-CoA pool formed after the addition of D-glucose, D-fructose, D-m annose, glycerol, or sorbitol, but there was little change when L-gluc ose, sucrose, maltose, succinate, or acetate was added, The beta-anome r of D-glucose was assimilated 10 times faster than the alpha-anomer, Intracellular CoA pools also changed with stress: in the pH, incubatio n temperature, or with osmotic stress. The sizes and compositions of C oA pools were not affected by pH changing between 4 and 8, but the bre akdown of acetyl-CoA and CoASH was greater at pH 9 than at pH 4 to 8. Production of acetyl-CoA was greatest at 40 degrees C, and at 50 degre es C, an acetyl-CoA pool did not form at all and the size of the CoASH pool declined. When the organism was stressed by the addition of NaCl at concentrations of more than 0.6 M, little acetyl-CoA was produced. The total CoA pool (the sum of the concentrations of CoASH, acetyl-Co A, and malonyl-CoA) remained within the limits of 0.83-1.40 nmol/mg of dry cell weight (0.30-0.52 mM). Whenever acetyl-CoA increased, CoASH decreased. Therefore, the acetyl-CoA/CoASB ratio is an important index of facultative anaerobes that reflects the state of carbon and energy metabolism in vivo.