Partial Characterization of the Alkylglycerol Cleavage Enzyme System of Rat Liver

Abstract

Abstract Subcellular distribution and cofactor requirements of the alkylglycerol cleavage enzyme system of rat liver have been investigated. The bulk of the enzyme system could not be removed from the microsomal fraction by washing procedures. Reduced glutathione (10 mm) increased the extent of the reaction 5-fold. The optimal concentration of ammonium sulfate was 4.8 mm. Ammonium ions increased the extent of the reaction and in addition appeared to activate the enzyme. Several other cations and anions did not stimulate the enzyme. Reduced pteridine was absolutely required for enzyme activity and the optimal concentration was 1.25 mm. The cleavage activity was stimulated 1.2-fold by NAD+ or NADH; NADP+ and NADPH had no effect. In the presence of near optimal concentrations of all known cofactors, rat liver-soluble fraction stimulated the cleavage activity 1.4- to 1.5-fold. The stimulation was produced by a heat-labile, nondialyzable component. The optimum pH for the reaction is approximately 9.0. In the absence of added pyridine nucleotides the long chain products of the cleavage reaction are aldehydes. Fatty acids were formed in the presence of the reduced as well as the oxidized nucleotides in this crude system and fatty alcohols were isolated only in the presence of NADH.