Composition and biosynthesis of molecular species of retina phosphoglycerides.
Recent studies on the fatty acid composition and labeling by glycerol of individual molecular species of retinal phosphoglycerides are presented. Docosahexaenoate-containing species are important constituents of retina phospholipids. 22:6 and saturated fatty acids appear in similar amounts in hexaenes (nearly 50% each). Very high percentages of 22:6 and other polyenoic fatty acids are found in molecular species containing negligible amounts of saturated fatty acids, indicating the occurrence of dipolyunsaturated phosphoglycerides, including didocosahexaenoate. On the other extreme, fully saturated species occur. 22:6-containing species are synthesized at high rates in most phosphoglycerides including phosphatidylinositol, which is mainly formed by tetraenoic classes. Oligoenes and saturates are synthesized de novo and once formed they may serve as precursors of others (e.g. tetraenes) by acyl-exchange reactions. Propranolol induces rapid modifications in the de novo biosynthesis of retina glycerolipids. Oligoenes and saturates are the most stimulated species in PI and PS, and the most inhibited ones in PC. In PE, the labeling of these species is stimulated, while the polyenes are inhibited. This remarkable example of metabolic heterogeneity in a single phosphoglyceride opens new possibilities in the study of the regulation of retinal membrane lipid biosynthesis.
Aveldaño de Caldironi
M I
MI
Instituto de Investigaciones Bioquímicas, Universidad Nacional del Sur y Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, Argentina.
Bazán
N G
NG