Fatty Acid Synthetase from Pig Liver

Abstract

An enzyme, exhibiting NADPH‐dependent oxidoreductase activity towards alicyclic ketones, has been extracted from pig liver and purified 122‐fold with respect to the protein contained in the crude extract after centrifugation at 54000×g. General properties, ultraviolet spectrum, stability, kinetic constants ( V and K m ) for NADPH and for typical substrates are reported. The molecular weight of the enzyme was estimated at 500000 by gel‐filtration. The enzyme is H s (H B )‐specific with respect to coenzyme. Alicyclic ketones can be conveniently used to measure the activity at all stages of purification. The topography of the active site responsible for oxidoreductase activity has been investigated by use of rigid alicyclic ketones such as trans ‐decal‐1‐ones as probes. In the accompanying paper it is shown (1) that the biological function of the whole enzyme complex is that of a fatty acid synthetase and (2) that the oxidoreductase activity can be ascribed to its 3‐oxoacyl‐acyl‐carrier protein reductase component.