Metabolism of brain glycolipid fatty acids.

The metabolism of the fatty acid moieties of brain cerebrosides, sulfatides, and gangliosides is reviewed and discussed. The methodology involved in the isolation of the fatty acids is described briefly. It seems clear now that most of these acids are made by chain elongation of intermediate length fatty acids by addition of acetate residues. The unsaturated acids are made by desaturation of the intermediate length acids (palmitic, heptadecanoic, stearic) followed by chain elongation. The hydroxy acids are made directly from the corresponding nonhydroxy acids, saturated, unsaturated, and odd-numbered. All the hydroxy acids undergo oxidative decarboxylation to yield fatty acids containing one less carbon atom. The odd-numbered acids are also made from propionate, which is elongated to intermediate length acids and then to longer acids. The major intermediate length "primer" acid seems to be palmitate, but there is evidence that the stearate used for cerebroside synthesis is also madede novo from acetate. The ganglioside fatty acids were found to turn over somewhat faster than the other fatty acids. Two metabolic pools for the cerebroside acids were found, one with a very high turnover rate, the other with a very low turnover rate.