Site‐directed mutagenesis of a fatty acid elongase ELO‐like condensing enzyme

The condensation step of fatty acid elongation is the addition of a C 2 unit from malonyl‐CoA to an acyl primer catalyzed by one of two families of enzymes, the 3‐ketoacyl‐CoA synthases and the ELO‐like condensing enzymes. 3‐Ketoacyl‐CoA synthases use a Claisen‐like reaction mechanism while the mechanism of the ELO‐catalyzed condensation reaction is unknown. We have used site‐directed mutagenesis of Dictyostelium discoideum EloA to identify residues important to catalytic activity and/or structure. Mutation of highly conserved polar residues to alanine resulted in an inactive enzyme strongly suggesting that these residues play a role in the condensation reaction.