1.14.19.26 A181T/A188G/Y189F/S205N/L206T/G207A the mutation yields an enzyme that functions primarily as a DELTA9-18:0-[acyl-carrier protein] desaturase. This enzyme displays only DELTA9 desaturase activity with 18:0-[acyl-carrier protein] and is nearly 4-fold more active with this substrate than with 16:0-[acyl-carrier protein]. Like mutant A181TyA200F, this enzyme retains DELTA6 desaturase activity with 16:0-[acyl-carrier protein] 1.14.19.26 A181T/A200F the mutation gives rise to an enzyme that catalyzed primarily the DELTA9 desaturation of 18:0-[acyl-carrier protein], but functions as a DELTA6 desaturase with 16:0-[acyl-carrier protein] 1.14.19.26 A181T/A200F/S205N/L206T/G207A replacement of specific amino acid residues in a DELTA6-palmitoyl (16:0)-[acyl-carrier protein] desaturase with their equivalents from a DELTA9-stearoyl (18:0)-[acyl-carrier protein] desaturase. The A181T/A200F/S205N/L206T/G207A mutant enzyme is functions principally as a DELTA9-18:0-[acyl-carrier protein] desaturase 1.14.19.26 A188G/Y189F mutant with broadened fatty acid chain-length specificity 1.14.19.26 additional information replacement of specific amino acid residues in a DELTA6-palmitoyl (16:0)-[acyl-carrier protein] desaturase with their equivalents from a DELTA9-stearoyl (18:0)-[acyl-carrier protein] desaturase, mutant enzymes are identified that have altered fatty acid chain-length specificities or that can insert double bonds into either the DELTA6 or DELTA9 positions of 16:0- and 18:0-[acyl-carrier protein]