Members of the Arabidopsis FAE1-like 3-Ketoacyl-CoA Synthase Gene Family Substitute for the Elop Proteins ofSaccharomyces cerevisiae

Shilpi Paul, Kenneth Gable, Frédéric Beaudoin, Edgar Cahoon, Jan Jaworski, Johnathan A. Napier, Teresa M. Dunn
2006 Journal of Biological Chemistry  
Several 3-keto-synthases have been studied, including the soluble fatty acid synthases, those involved in polyketide synthesis, and the FAE1-like 3-ketoacyl-CoA synthases. All of these condensing enzymes have a common ancestor and an enzymatic mechanism that involves a catalytic triad consisting of Cys, His, and His/Asn. In contrast to the FAE1-like family of enzymes that mediate plant microsomal fatty acid elongation, the condensation step of elongation in animals and in fungi appears to be
more » ... iated by the Elop homologs. Curiously these proteins bear no resemblance to the well characterized 3-keto-synthases. There are three ELO genes in yeast that encode the homologous Elo1p, Elo2p, and Elo3p proteins. Elo2p and Elo3p are required for synthesis of the very long-chain fatty acids, and mutants lacking both Elo2p and Elo3p are inviable confirming that the very long-chain fatty acids are essential for cellular functions. In this study we show that heterologous expression of several Arabidopsis FAE1-like genes rescues the lethality of an elo2⌬elo3⌬ yeast mutant. We further demonstrate that FAE1 acts in conjunction with the 3-keto and trans-2,3-enoyl reductases of the elongase system. These studies indicate that even though the plantspecific FAE1 family of condensing enzymes evolved independently of the Elop family of condensing enzymes, they utilize the same reductases and presumably dehydratase that the Elop proteins rely upon. Cytosolic fatty acid synthases catalyze the de novo synthesis of the majority of cellular fatty acids, which have 16 or 18 carbons. However, there are many other types of fatty acids in the cellular lipids, including the very long-chain fatty acids (VLCFA) 2 that are synthesized through elongation of the C16 or C18 fatty acid by a microsomal enzyme system. The VLCFAs have been implicated in a number of cellular processes, including the formation of nuclear pores, trafficking of lipids and proteins, and the formation of membrane domains that organize signaling proteins. In higher plants, VLCFAs are critical components of the waxes
doi:10.1074/jbc.m507723200 pmid:16449229 fatcat:bdk4viisgzfl5dbja5wqzwcq2q