Exposure of major neutral glycolipids in red cells to galactose oxidase

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Abstract
The exposure of several major red-cell glycolipids to galactose oxidase was studied by oxidizing the cells with the enzyme and reducing them with NaB2H4. After isolation, the deuterium label was detected by mass fragmentography. 60–70% globoside in human and porcine erythrocytes was exposed as measured by this method. In contrast, asialo-GM2 in guinea-pig erythrocytes and Forssman glycolipid in sheep erythrocytes were mainly in a cryptic state. Neuraminidase treatment increased the incorporation of deuterium label to asialo-GM2 4–8-fold. A similar effect was seen in Forssman glycolipid when sheep red cells were labeled with the neuraminidase/galactose oxidase/NaB3H4 method. In contrast, the increase in labeling was only about 10–40% in porcine and human globosides, which were efficiently exposed to galactose oxidase already in native red cells.