The Lipid Library

SULFONOLIPIDS

STRUCTURE, OCCURRENCE AND BIOSYNTHESIS

The best known and most abundant of the sulfonolipids is sulfoquinovosyldiacylglycerol or 1,2-di-O-acyl-3-O-(6'-deoxy-6'-sulfo-α-D-glucopyranosyl)-sn-glycerol, which is a key component of the photosynthetic mechanism of higher plants and other photosynthetic organisms. Because of its biosynthetic and functional relationship to the mono- and digalactosyldiacylglycerols, it is discussed in those web pages.

In 1978,the marine diatom, Nitzschia alba, was found to contain a number of interesting sulfolipids as membrane constituents, i.e. 24-methylene-cholesterol sulfate, 1-deoxyceramide-1-sulfonate and phosphatidylsulfocholine (a sulfonium analogue of phosphatidylcholine), in addition to sulfoquinovosyldiacylglycerol. The last is present in an amount comparable to that in higher plants, although the organism is non-photosynthetic.

1-Deoxyceramide-1-sulfonate consists of a long chain-base, analogous to sphingosine but with a sulfonate moiety attached to carbon 1. The predominant fatty acid (64%) is trans-3-hexadecenoic acid, which is normally associated with the phosphatidylglycerol of plant chloroplasts. Experiments with 35S-cysteine or cystine labeled the deoxyceramide sulfonate and phosphatidylsulfocholine, but not the sterol sulfate nor the sulfoquinovosyldiacylglycerol. The illustration show negatively charged molecules but there will of course be balancing cations under natural conditions.

Phosphatidylsulfocholine, with two methyl groups attached to the sulfur atom as opposed to three attached to nitrogen, completely replaces phosphatidylcholine in Nitzschia alba. However, it has subsequently been found in other marine diatoms and algae that also contain phosphatidylcholine. Experiments with isotopically labelled substrates in Nitzschia alba confirmed that both methyl groups and the sulfur atom were derived from methionine.

Subsequently, a sulfonic acid derivative of ceramide, N-fatty acyl capnine or capnoid, was described from gliding bacteria of the genera Cytophaga, Capnocytophaga, Sporocytophaga, and Flexibacter. These are organisms that are able to move over solid surfaces, but not through liquids, although they do not appear to have flagella or other organs of propulsion. Capnine is 2-amino-3-hydroxy-15-methylhexadecane-1-sulfonic acid and occurs in the organisms both in the free form and as N-acylated derivatives, though up to 20% of other homologues can occur, depending on species. The fatty acids are much more heterogeneous and vary from C₁₄ to C₁₆ in chain-length, a high proportion with iso- or anteiso-methyl branches and hydroxyl groups in positions 2 and 3. Related compounds, termed sulfobacins A and B, i.e. (2R,3R)-3-hydroxy-2-[(R)-3-hydroxy-15-methylhexadecanamido]-15-methylhexadecanesulfonic acid and (2R,3R)-3-hydroxy-15-methyl-2-[13-methyltetradecanamido]-hexadecanesulfonic acid, respectively, have been found in Chryseobacterium sp. Similar lipids have been found in the gram-negative, sea-water bacterium Cyclobacterium marinus.

The experimental evidence suggests that biosynthesis of capnine in these bacteria occurs by the condensation of 13-methylmyristoyl-coenzyme A with cysteic acid, in a manner analogous to the condensation of palmitoyl-coenzyme A with serine during the biosynthesis of sphingoid bases. The function of capnoids is obscure, but there are suggestions that they may have a role in the motility of the organisms.

Recently, a new sulfonolipid with some structural affinity to the capnoids, has been isolated from a halophilic aerobic bacterium, Salinibacter ruber. It has the structure 2-carboxy-2-amino-3-O-(13'-methyltetradecanoyl)-4-hydroxy-18-methylnonadec-5-ene-1-sulfonic acid, and represents about 10% of the total cellular lipids.

Taurolipids: A number of lipids have been found that are conjugated to taurine (ethanolaminesulfonic acid), of which the best known are certain bile acids, which are discussed elsewhere on this site as are N-acyltaurines of mammalian origin. Aside from the bile acids, the first taurolipids to be recognized were novel C₁₈ hydroxy acids (3, 4 or 5 hydroxyl groups) with an amide link to taurine from the ciliated protozoan Tetrahymena. The hydroxyl on carbon 3 is acylated with normal fatty acids (approx. 30% 16:0), and in one variant, carbon 7 is similarly acylated. The deacylated backbone has been termed ‘lipotaurine’.

Biosynthesis is believed to involve conjugation of stearic acid with taurine, with subsequent sequential insertion of hydroxyl groups.

Recently, a biologically active taurine-containing lipid, termed 'irciniasulfonic acid B', was isolated from a marine sponge, Ircinia sp. This comprised 3-methyl-8-hydroxy-dec-2-enoic acid conjugated to taurine, with various unusual fatty acids linked to the hydroxyl group.

In addition, a tauroglycolipid, 1,2-diacyl-3-glucuronopyranosyl-sn-glycerol taurineamide, was isolated from a seawater bacterium Hyphomonas jannaschiana, which has the further unusual feature of an absence of phospholipids. The main fatty acyl chains are saturated and monoenoic (C₁₆ to C₂₀).

An unusual ganglioside, taurine-conjugated GM₂, was isolated from brain samples from patients with Tay-Sachs disease, a well-known glycosphingolipid (GSL) storage disease. In this unusual lipid, the carboxyl group of N-acetylneuraminic acid is amidated by taurine. As this lipid is not present in normal brains, it seems probable that it is associated with the pathogenesis of the disease, possibly as a means of removing the excess of GM₂ from the tissue.

Recommended Reading

• Anderson, R., Kates, M. and Volcani, B.E. Identification of the sulfolipids in the non-photosynthetic diatom Nitzschia alba. Biochim. Biophys. Acta, 528, 89-106 (1978).
• Bisseret, P., Ito, S., Tremblay, P.A., Volcani, B.E., Dessort, D. and Kates, M. Occurrence of phosphatidylsulfocholine, the sulfonium analog of phosphatidylcholine in some diatoms and algae. Biochim. Biophys. Acta, 796, 320-327 (1984).
• Corcelli, A., Lattanzio, V.M.T., Mascolo, G., Babudri, F., Oren, A. and Kates, M. Novel sulfonolipid in the extremely halophilic bacterium Salinibacter ruber. Appl. Env. Microbiol., 70, 6678-6685 (2004).
• Godchaux, W. and Leadbetter, E.R. Sulfonolipids of gliding bacteria. Structure of the N-acylaminosulfonates. J. Biol. Chem., 259, 2982-2990 (1984).
• Kaya, K. Chemistry and biochemistry of taurolipids. Prog. Lipid Res., 31, 87-108 (1992).
• Li, Y.T., Maskos, K., Chou, C.W., Cole, R.B. and Li, S.C. Presence of an unusual GM₂ derivative, taurine-conjugated GM₂, in Tay-Sachs brain. J. Biol. Chem., 278, 35286-35291 (2003).

Updated: 12/11/2006 Credits/disclaimer	Scottish Crop Research Institute (and MRS Lipid Analysis Unit), Invergowrie, Dundee (DD2 5DA), Scotland