Exposure of the major human red-cell glycolipid, globoside, to galactose oxidase

Abstract

Plasma membrane glycolipids were localized at the outer leaflet of the lipid bilayer, and their carbohydrate portions were exposed to the environment. The efficiency of exposure, however, was not known. The availability of the major red cell glycolipid, globoside, to externally added galactose oxidase was able to be determined. Red cells were extensively treated with the enzyme and the oxidized cells reduced with NaBD4. After isolation the extent of exposed globoside was estimated by mass spectrometry. The exposure of globoside varies in red cells of different individuals from 37-66%. The fatty acid composition of externally available globoside was the same as that of nonoxidized globoside. The exposure was not influenced by protease treatment of intact cells and no correlation was found with different ABO blood groups.