Branched long-chain bases from the bivalve Corbicula sandai

The glycosylceramides of the nematode Caenorhabditis elegans contain an unusual, branched-chain sphingoid base

Caenorhabditis elegans was cultured in semi-defined medium containing yeast extract, soy peptone, glucose, hemoglobin, Tween 80, and sitosterol. Monoglycosylceramides were chromatographically purified from nematode extracts. Their structures were elucidated with mass spectrometry, nuclear magnetic resonance spectroscopy, and analysis of methanolysis products of the parent cerebrosides. The glycosylceramides were unusual in that the only long-chain sphingoid base detected was an iso-branched compound with a C-4 double bond (i.e., 15-methyl-2-aminohexadec-4-en-1,3-diol). Glucose was the only sugar moiety detected. The fatty acids consisted of a series of primarily straight-chain, saturated, 2-hydroxylated C20-C26 acids; some iso-branched analogs also occurred. The sphingomyelins of C. elegans were also hydrolyzed, and the same iso-branched C17 compound was the only sphingoid base detected. This is the first structural analysis of a nematode glycosphingolipid and the first report of an organism in which the long-chain sphingoid bases are entirely iso-branched.

Characteristic constituents of glycolipids from frog brain and sciatic nerve

Cerebroside, sulfatide, monoglycosyl glyceride, and ester cerebroside were isolated from frog brain and sciatic nerve, and their distribution and chemical constituents were determined. The long-chain base compositions of cerebroside, sulfatide, and ester cerebroside were unique in the presence of branched-base components (5-15% of the total bases) and in the abundance of saturated dihydroxy base components (15-45% of the total). The amount of branched long-chain bases was greater in sciatic nerve than in brain. The hexose composition of the glycolipids consisted entirely of galactose except for brain cerebroside, in which a small amount of glucose was detected. Monogalactosyl glyceride consisted of the diacyl and alkylacyl forms, in a molar ratio of 81:19 for brain and 62:38 for sciatic nerve. The fatty acid composition of glycosphingolipids was characterized by the predominance of hydroxy and nonhydroxy 24:1 acids, and the concentration of 24:0 was extremely low. The proportion of unsaturated fatty acids accounted for 80% of the total. Major fatty acids of monogalactosyl glyceride were palmitic, oleic, stearic, and palmitoleic acids; the highest concentration was that of palmitic acid. Ester cerebroside was separated into three subfractions mainly on the basis of the proportion of hydroxy and nonhydroxy components in the amide-linked fatty acids.

Identification of beta-D-mannosylceramide in hepatopancreas of the fresh-water bivalve, Hyriopsis schlegelii

A mannosylceramide was isolated by preparative thin-layer chromatography on a 3% borate-impregnated silica gel plate from a monohexosylceramide fraction of the hepatopancreas of the fresh-water bivalve, Hyriopsis schlegelii. It contained only mannose as the sugar component and the ceramide moiety contained mainly sphingosine and palmitic acid. Anomeric configuration of the sugar moiety was determined by enzymatic hydrolysis with beta-D-mannosidase. The concentration of this glycolipid was 5% of the total monohexosylceramide fraction of the hepatopancreas.

Characterization of cerebroside (monoglycosylceramide) from the sea anemone, Metridium senile. Identification of the major long-chain base as an unusual dienic base with a methyl branch at a double bond

1. Cerebroside of the sea anemone, Metridium senile, has been isolated (0.6 mg/g dry tissue weight) and structurally characterized. 2. The structure was shown by mass spectrometry, NMR spectroscopy and degradative studies as beta-glucopyranosylceramide. The major fatty acids were 16 : 0 and 20 : 0 D-2-hydroxy fatty acids. The major base was a novel base, D-erythro-1,3-dihydroxy-2-amino-9-methyl-trans-4, trans-8-octadecadiene. 3. Some unusual fatty acids of marine origin are suggested to originate in this long-chain base by metabolic conversion. 4. The implication of the methyl branch position of the base on our current view of sphingolipid function in the plasma membrane is discussed.