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The Metabolism of Glyceride Glycolipids

1970; Elsevier BV; Volume: 245; Issue: 10 Linguagem: Inglês

10.1016/s0021-9258(18)63100-x

1083-351X

David A. Wenger, Kalluri Subba Rao, Ronald A. Pieringer, With the technical assistance of Joan W. Petitpas,

Diet, Metabolism, and Disease

Abstract Particulate enzyme preparations of brain from rats greater than 11 days of age catalyze the synthesis of digalactosyl diglyceride from two common precursors, UDP-galactose and diglyceride. Monogalactosyl diglyceride has been implicated as an intermediate in the reaction. Sodium deoxycholate at optimum concentrations is required for the incorporation of UDP-14C-galactose (uniformly labeled) but not for the incorporation of diglyceride-[1,3-14C-glycerol] or exogenous monogalactosyl diglyceride (uniformly labeled 14C-galactose) into digalactosyl diglyceride. Five structurally related bile salts and a variety of other types of detergents do not effectively substitute for deoxycholate. Sodium deoxycholate, which does not serve as a substrate in this reaction, appears to function as a surface-active adjuvant that promotes an interaction between UDP-galactose, enzyme, and an endogenous monogalactosyl diglyceride. Of seven diglycerides tested some preference is shown for dipalmitin as a substrate. Experiments carried out with specific α- and β-galactosidases suggest that the anomeric carbon atom of the galactose to galactose bond of the galactolipid is of the α-configuration. This α-galactosidic bond appears to be unique to the glycolipids thus far characterized and isolated from the central nervous system. The activity of the biosynthetic enzyme is dependent on the age of the rat from which the brain was taken; it is low or nonexistent before about 11 days, but increases sharply after this time until reaching a peak at 16 to 18 days postpartum. Since the age of most active myelination (about 10 to 20 days) in the rat is coincident with the age of highest enzyme activity, a role in the process of myelination is suggested for the enzyme responsible for the synthesis of digalactosyl diglyceride.