The isolation and partial characterization of glycolipids of normal human leucocytes

Abstract

The lipids of purified human leukocytes were extracted with chloroform-methanol and the extract was washed with water. Glycolipids, isolated by Florisil chromatography, were subjected to mild alkaline hydrolysis and the alkali-resistant fraction was fractionated on a silicic acid column. Three classes of glycolipid were separated. The less polar, containing 3.6% of the total glycolipid hexose as galactose, was tentatively identified as ceramide monohexoside. The major glycolipid fraction was characterized as ceramide dihexosides. The more polar glycolipids comprised 1-6% of the total glycolipid hexose as galactose and glucose (in the molar ratio 2:1) and were non-acidic. This class was separated as a mixture containing ninhydrin-positive glycolipids. The ceramide dihexosides taken from two leukocyte preparations accounted for 15-2% and 16-4% by weight of the total lipids. The carbohydrate moiety of the ceramide dihexosides contained galactose and glucose in the molar ratio 2:1. Partial acid hydrolysis and paper chromatography indicated that the hexoses are present as disaccharides, lactose being identified as one of them. Palmitic acid (C16:0) and nervonic acid (C24:i) were the major fatty-acids of this glycolipid. Hydroxy fatty-acids were not detected.