Isolation of six novel phosphoinositol-containing sphingolipids from tobacco leaves

A concentrate of phosphosphingolipids from tobacco leaves has been resolved into two groups by chromatography on diethylaminoethylcellulose. The first group eluted contains no acetyl residues, whereas the second group contains one N-acetyl/mol of phosphorus. Three lipids from each group have been purified by chromatography on Porasil columns. The chemical composition of these six novel lipids shows them to be related to the previously characterized phosphosphingolipids PSL-I, N-acetylglucosamine[glucuronic acid, inositol phosphate]ceramide and PSL-II, glucosamine[glucuronic acid, inositol phosphate] ceramide [Kaul, K.,and Lester,R. L. (1975), Plant Physiol. 55, 120]. The novel lipids are: PSL-IA, PSL-I-[Ara2Gal2]; PSL-IB, PSL-I-[Ara3Gal2]; PSL-IC, PSL-I-[Ara4Gal2]; PSL-IIA, PSL-II-[Ara3Gal]; PSL-IIB, PSL-II-[Ara2or3Gal2]; PSL-IIC, PSL-II-[Ara2Gal2Man]. The unusual finding of unacetylated hexosamine in the PSL-II group of lipids appears not to be an artifact, as suggested by experiments involving rapid harvesting and processing of the tobacco leaves. Some of the fractions obtained by chromatography on diethylaminoethylcellulose appear to contain phosphosphingolipids with 16 or more sugar residues.