OCCURRENCE OF NONENZYMATIC N-ACETYLATION OF SPHINGANINE WITH ACETYL-COENZYME-A PRODUCING C-2-H-2-CERAMIDE AND ITS INCONVERTIBILITY TO APOPTOTIC C-2-CERAMIDE

Sphinganine, a biosynthetic precursor of ceramide, was nonenzymaticall y acetylated with acetyl coenzyme A at the C-2-amino residue to produc e C-2-H-2-ceramide (N-acetyl sphinganine) in an organic solvent and in an aqueous solution with a high yield, whereas sphingenine was only a cetylated slightly. The structure of the N-acetyl sphinganine was iden tified with mass spectrum, and with chromatography using an authentic N-acetylated substance. Furthermore, the C-2-H-2-ceramide ceramide was examined for enzymatic desaturation to determine whether C-2-ceramide , a cell-permeable ceramide responsible for apoptosis of cells, was pr oduced, revealing an inferior substrate for H-2-ceramide desaturase of horse brain microsomes.