Acylation of Naturally Occurring and Synthetic 1-Deoxysphinganines by Ceramide Synthase

• Published in: The Journal of biological chemistry 1998-07, Vol.273 (30), p.19060-19064
• Main Authors: Humpf, Hans-Ulrich, Schmelz, Eva-Maria, Meredith, Filmore I., Vesper, Hubert, Vales, Teresa R., Wang, Elaine, Menaldino, David S., Liotta, Dennis C., Merrill, Alfred H.
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.273.30.19060

Fumonisin B 1 (FB 1 ) is the predominant member of a family of mycotoxins produced by Fusarium moniliforme (Sheldon) and related fungi. Certain foods also contain the aminopentol backbone (AP 1 ) that is formed upon base hydrolysis of the ester-linked tricarballylic acids of FB 1 . Both FB 1 and, to a lesser extent, AP 1 inhibit ceramide synthase due to structural similarities between fumonisins (as 1-deoxy-analogs of sphinganine) and sphingoid bases. To explore these structure-function relationships further, erythro - and threo -2-amino, 3-hydroxy- (and 3, 5-dihydroxy-) octadecanes were prepared by highly stereoselective syntheses. All of these analogs inhibit the acylation of sphingoid bases by ceramide synthase, and are themselves acylated with V max / K m of 40–125 for the erythro -isomers (compared with approximately 250 for d - erythro -sphinganine) and 4–6 for the threo -isomers. Ceramide synthase also acylates AP 1 (but not FB 1 , under the conditions tested) to N -palmitoyl-AP 1 (PAP 1 ) with a V max / K m of approximately 1. The toxicity of PAP 1 was evaluated using HT29 cells, a human colonic cell line. PAP 1 was at least 10 times more toxic than FB 1 or AP 1 and caused sphinganine accumulation as an inhibitor of ceramide synthase. These studies demonstrate that: the 1-hydroxyl group is not required for sphingoid bases to be acylated; both erythro - and threo -isomers are acylated with the highest apparent V max / K m for the erythro -analogs; and AP 1 is acylated to PAP 1 , a new category of ceramide synthase inhibitor as well as a toxic metabolite that may play a role in the diseases caused by fumonisins.