PLANT MICROSOMAL PHOSPHOLIPASES EXHIBIT PREFERENCE FOR PHOSPHATIDYLCHOLINE WITH OXYGENATED ACYL-GROUPS

Microsomal preparations from developing rape (Brassica napus) embryos, young wheat (Triticum aestivum) roots and ripening avocado (Persea americana) mesocarp metabolized added sn-2-[C-14]ricinoleoyl phosphatidylcholine (PC) and sn-2-[C-14]linoleoyl-hydroperoxide-PC into [C-14]fatty acids, [C-14]diacylglycerols and [C-14]phosphatidic acids at a higher rate than added sn-2-[C-14]oleoyl PC and sn-2-[C-14]linoleoyl-PC substrates, thereby demonstrating a specificity of plant microsomal phospholipases towards PC with oxygenated acyl groups. The release of [C-14]fatty acids was, in rape and wheat membranes, largely independent of addition of Ca2+ or EGTA whereas the production of [C-14]diacylglycerols and [C-14]phosphatidic acids was strongly inhibited by EGTA but this inhibition was relieved by excess of Ca2+. The relative preference of the different lipases for hydroxylated and peroxidated acyl groups differed widely between the different species.