COENZYME-A ACTIVATION OF ACETYL-COA CARBOXYLASE

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  • 1 January 1981
    • journal article
    • research article
    • Vol. 256  (5) , 2289-2296
Abstract
Acetyl-CoA carboxylase is activated by physiological concentrations of CoA. Activation of partially purified enzyme by CoA is accompanied by a decrease in the Km for acetyl-CoA from 0.2 mM to about 4 .mu.M, which is the physiological concentration of acetyl-CoA in the cytosol. CoA activation of the purified enzyme is accompanied by an increase in the Vmax, without changing the Km for acetyl-CoA. The Km for acetyl-CoA of the purified enzyme is about 10-40 .mu.M. The purification procedure results in a decrease in the Km for acetyl-CoA; under these conditions, CoA activation does not cause further lowering of the Km. CoA activation is accompanied by polymerization of the enzyme. CoA activation is not causally related to polymerization; there is 1 CoA binding site/subunit of acetyl-CoA carboxylase. CoA binding at that site is not affected by the presence of citrate, but palmityl-CoA inhibits CoA binding. CoA alone cannot reverse palmityl-CoA inhibition of the carboxylase but bovine serum albumin and CoA together can activate the palmityl-CoA-inhibited enzyme. The involvement of bovine serum albumin-like protein, CoA and palmityl-CoA may play a physiologically significant role in the control of acetyl-CoA carboxylase.