The biocleavage of isomeric glyceryl ethers by soluble liver enzymes in a variety of species

Abstract

We have examined the biocleavage of glyceryl ethers in cell-free liver preparations from rats, dogs, guinea pigs, gerbils, mice, hamsters, rabbits, and slugs. Our data confirmed earlier work showing that the co-factor requirements for this cleavage in rat liver are pteridine, O 2, and NADPH. We also demonstrated that the enzyme system involved can readily be washed away from the microsomes. This soluble ether-cleaving enzymatic system, characterized by electron microscopy and zonal centrifugation, cleaved the 2-isomers and the C 16:0 chain to a slightly greater extent than the 1-isomers and the C 18:0 chain. When NAD + was present in the reaction mixture, the principle 14C products were fatty acids and fatty alcohols; palmitic acid was formed from the C 16:0 glyceryl 1-ether, and stearic acid was formed from the C 18:0 glyceryl 1-ether. When we omitted NAD + from the reaction mixture, 14Clabeled fatty aldehydes and fatty alcohols built up and 14C-labeled fatty acids decreased. The NADPH, required for the reduction of the pteridine co-factor involved in ether cleavage, also appears to be required for the reduction of the fatty aldehyde to the alcohol. Only the liver and intestine possessed significant quantities of the ethercleaving enzyme, and its activity varied considerably among species.