The lipid residues in cytolipin H

Abstract

SUMMARY Analyses were done of the individual fatty acids in two preparations of cytolipin H and the lipid bases in one preparation. A number of fatty acids were present, lignoceric acid predominating. No 2-hydroxy fatty acids were present. Of the lipid bases, 93% wm sphingosine and 7% was a more unsaturated residue (dehydrosphingosine?) . No dihydrosphingosine was present. Analyses of a number of cytolipin preparations showed them to be similar to cerebrosides derived from nonnervous animal tissues in having a nonuniform distribution of normal saturated fatty acids: Cz4, Czz, and Cle acids were present in high concentration, and (320, C,, and C1, acids were present in very low concentration. on the basis of elementary and group analyses, cytolipin H, a lipid hapten isolated from human epidermoid carcinoma, was reported to contain fatty acid, a Iipid base, glucose, and galactose in equimolar proportions (1). The carbohydrate residues were recently found to have the configuration of the disaccharide 4-O-~-D-galactopyranosyl-D-glucopyranose (lactose) (2). However, although evidence was presented indicating the presence of both fatty acid and a long-chain base, the lipid residues were not identified. A close correspondence of the carbon content of cytolipin H with that calculated for a molecule containing cerebronic acid and sphingosine led to the suggestion that these residues did indeed constitute the lipid portion of the cytolipin H molecule. It was subsequently found that 2-hydroxy fatty acids were absent. Scarcity of material prevented a conventional solution to this problem at the time, and micromethods had to be developed that would permit analysis of the fatty acid content of the original sample. A second specimen of cytolipin H was analyzed with respect to both its fatty acids and the long-chain base. These studies are presented in this report.