DESATURATION PROCESSES IN FATTY-ACID AND ACYL LIPID BIOSYNTHESIS

Plant fatty acid desaturases require molecular oxygen and a reduced pyridine nucleotide. Most systems are composed of several membrane-bound proteins and were studied in endoplasmic reticulum or chloroplasts; a noticeable exception is stearoyl-ACP desaturase, a soluble enzyme localized in the stroma of chloroplasts. The c-DNA corresponding to this enzyme has been sequenced from several plant species. Several molecular species of oleoyl-phosphatidylcholine were directly accepted as substrates by the omega(6) desaturase from various plants. An omega(6) desaturase solubilized from spinach envelopes accepted several molecular species of galactolipids as substrates. Linoleoyl-phosphatidylcholine was accepted as a substrate by an omega(3) desaturase in endoplasmic reticulum while linoleoyl-MGDG was a substrate for the omega(3) desaturase localized in chloroplast envelope.