Hochachka, P.W., Storey, K.B. and Baldwin, J. 1975. Squid muscle citrate synthase: control of carbon entry into the Krebs cycle. Comp. Biochem. Physiol. 52B, 193- 199.

SQUID MUSCLE CITRATE SYNTHASE: CONTROL OF CARBON ENTRY INTO THE KREBS CYCLE

P. W HOCHACHKA, K. B. STOREY and J. BALDWIN


Abstract
1. In squid mantle muscle, citrate synthase occurs in high specific activity as a large 250,000 MW multimeric enzyme.

2. The enzyme activity is extremely sensitive to NADH inhibition which is partially reversed by AMP. NADH causes a drastic reduction in the enzyme affinity for oxaloacetate.

3. Squid mantle citrate synthase is also sensitive to inhibition by ATP, alpha-ketoglutarate and citrate. ATP effects are competitive with respect to acetylCoA while citrate and alpha-ketoglutarate inhibit the enzyme by competing with oxaloacetate.

4. These regulatory properties are largely unaffected by pressure.