The identification of sulphatides in human erythrocyte membrane and their relation to sodium-potassium dependent adenosine triphosphatase.

Sulphatides (ceramide galactose-3-sulphate) were isolated from human erythrocyte membranes. The amount obtained was 3.3 mg from 6.7 kg of wet cells, or 1.5 X 10(-9) mol per g dry cells. The polar part was shown to be galactose-3-sulphate by chromatographic analysis, infrared spectrometry, and mass spectrometry after solvolytic desulphation. The ceramide part consisted of three major molecular species, sphingosine-palmitic acid, sphingosine-2-hydroxypalmitic acid, and phytosphingosine-2-hydroxypalmitic acid, as shown by thin-layer chromatography, mass spectrometry of galactosylceramides after desulphation, and gas chromatography of components after hydrolysis. The composition differed from other human erythrocyte sphingolipids. Although the amount of sulphatides is very low for erythrocyte, the ratio of sulphatide concentration and Na+-K+-ATPase activity [EC 3.6.1.3] is similar to the situation found for several animal tissues with an increased level of Na+ transport. This finding is discussed in relation to a recent model of sulphatide function in a transport unit for Na+ and K+ (cofactor site model).