The Involvement of Thioesterase Activity in Phospholipid Metabolism

Abstract

Crude soluble preparations obtained from anaerobic, light-grown cells of Rhodopseudomonas sphaeroides have been shown to possess a significant level of acyl-CoA thioesterase activity. This enzyme catalyzes the hydrolysis of long chain fatty acyl thioesters of coenzyme A to produce free fatty acids and release coenzyme A (1). Maximal velocities obtained for thioesterase activity utilizing the coenzyme A derivatives of the saturated fatty acid, palmityl-CoA, and the unsaturated fatty acid, oleoyl-CoA, indicate that the enzyme possesses no preference in relation to the degree of saturation of the substrate. Thioesterase activity monitored in asynchronously dividing cultures indicated that the activity increased proportional to cell growth in cells growing anaerobically at a light intensity of 500 ft-c. Following a shift from high (500 ft-c.) to low (50 ft-c.) intensity light, a marked decrease in thioesterase activity was observed. A similar decrease in thioesterase activity was observed just prior to cell division in cultures synchronized by a light shift procedure.