Studies on ali-esterases and other lipid-hydrolysing enzymes. 1. Inhibition of the esterases and acetoacetate production of liver

Abstract

The ali-esterases of rat liver are highly sensitive to inhibition by various alkyl phosphate derivatives such as diethyl p-nitrophenyl phosphate (E 600). They can be selectively inhibited in vivo by intramusc. injn. of tri-o-cresyl phosphate. Both the ali-esterases and the phospholipase are inhibited 60-70% by 10-2 [image] atoxyl. The lipase activity is not significantly affected either by the phosphate derivatives or by atoxyl concns. which inhibit ali-esterase activity. The spontaneous acetoacetate production, ali-esterase activity, and phospholipid hydrolysis of liver are all inhibited to a similar extent by atoxyl. Selective inhibition of ali-esterases by the phosphate derivatives in vitro or in vivo has no effect upon the acetoacetate production or O2 uptake of liver slices. The results fail to give any indication of an essential function of ali-esterases in the normal lipid metabolism of rat liver. The results tend to confirm the generally accepted theories regarding lipid oxidation in liver. The main pathway of lipid oxidation would involve, first, hydrolysis of phospholipin, and secondly, oxidation of the free fatty acids liberated.