Studies on the Biosynthesis of the O-Alkyl Bond in Glycerol Ether Lipids

Abstract

The ether bond in glycerol ether lipids is biosynthesized₁via the reaction of 1-acyl dihydroxyacetone-3-phosphate (acyl DHAP) with long chain alcohol to form 1-0-alkyl dihydroxyacetone-3phosphate (alkyl DHAP) (1–3). Alkyl DHAP, like its counterpart acyl DHAP, is then enzymatically reduced by NADPH to form 1-0-alkyl glycerol-3-phosphate (alkyl G-3-P) (4). Alkyl G-3-P is subsequently acylated to form the ether analog of phosphatidic acid (5), which is then converted to phosphorylcholine-and phosphorylethanolaminecontaining glycerol ether lipids via the Kennedy pathway (6,7). A number of workers have shown that plasmalogens are biosynthesized via the direct dehydrogenation of different glycerol ether lipids (for a review, see Ref. 8). Therefore, it seems that the reaction catalysed by the alkyl DHAP synthase, ie. the reaction of acyl DHAP with long chain alcohol, is the primary reaction by which the ether bond is introduced into all glycerol ether lipids. Studies on some of the properties of this enzyme are described here.