Abstract
The galactolipid, phospholipid, and fatty acid composition of chloroplast envelope membrane fractions isolated from leaves of Vicia faba L. has been determined. The major lipids in this fraction are: monogalactosyldiglyceride, 29%; digalactosyldiglyceride, 32%; phosphatidylcholine, 30%; and phosphatidylglycerol 9%. The lipid composition of the chloroplast envelope membranes is qualitatively similar to that of the lamellar membranes isolated from the same plastids, but the proportion of each lipid present is very different. The total galactolipid to total phospholipid ratio was 1.6: 1 in the envelope and 11.1: 1 in the lamellae. The monogalactosyldiglyceride-digalactosyl-diglyceride ratio was 0.9: 1 in the envelope and 2.4: 1 in the lamellae. Both membranes lack phosphatidylethanolamine.Linolenic acid is the major fatty acid in the envelope lipids representing 63% of the total fatty acid, whereas in the lamellae it represents 83%. The same fatty acids are present in both the envelope and lamellar lipids except the trans-Delta(3)-hexadecenoic acid, which is confined to the lamellar lipids, particularly the phospholipid fraction.A quantitative comparison of the lipid and fatty acid compositions of the envelope with those of mitochondrial and microsomal fractions indicates that the chloroplast envelope has a composition intermediate between that of the chloroplast lamellae and these extrachloroplastic membranes.