Relationships of chain lengths and double bond locations in O-alkyl, O-alk-1-enyl, acyl, and fatty alcohol moieties in preputial glands of mice

Abstract

Wax esters, glyceryl ether diesters, triglycerides, and sterol esters are the major lipid classes present in normal preputial glands of mice. Small amounts of phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) were also found. Three-fourths of the PE fraction was comprised of alk-1-enyl ethers, whereas most of the PC fraction (⋍90%) was present in the diacyl form. The ether linkage was found to be at the 1-position of glycerol. The chain lengths of the alkyl and alk-1-enyl hydrocarbon moieties of glyceryl ether diesters, phosphatidyl choline, and phosphatidyl ethanolamine were similar to one another and to the alcohol moieties of the waxes. Principal hydrocarbon chains in ether linkage with glycerol were 14:0, 14:1, 16:0, and 16:1. The location of double bonds in the acyl, alkyl, and alk-1-enyl hydrocarbon moieties of the various lipid classes was determined by gas-liquid chromatography of the aldehyde fragments produced by reductive-ozonolysis. The 18:1 acyl moieties from the triglycerides and waxes consisted primarily of the Δ-9 isomer but small amounts of the Δ-11 isomer were also found. The 16:1 acyl moieties of triglycerides were also mainly the Δ-9 isomer, whereas in waxes the 16:1 acyl moieties were equally divided between Δ-6 and Δ-9 isomers. Location of double bonds in the 16:1 and 14:1 alcohol and acyl moieties of waxes and the alkyl moieties of glyceryl ether diesters was similar. The 16:1 fraction was comprised mainly of the Δ-6 isomer and smaller quantities of the Δ-7 and Δ-9 isomers. The Δ-5 and Δ-6 isomers accounted for more than 90% of the 14:1 chains in the fatty alcohols of waxes and in the alkyl moieties of glyceryl ether diesters; the acyl moieties of waxes contained approximately 70% of these isomers. The data indicate that in preputial glands of mice the intermediary pathways or enzymatic sites responsible for the biosynthesis of fatty alcohol, and to some extent fatty acids, in the waxes must be identical to those pathways or sites responsible for the biosynthesis of the alkyl chains of glyceryl ether diesters. The similarities of alkyl and alk-1-enyl ether-linked hydrocarbon moieties suggest that these two classes of lipids can be interconverted enzymatically.