Mutagenesis of the borage Delta(6) fatty acid desaturase

The consensus sequence of the third histidine box of a range of Delta (5), Delta (6), Delta (8) and sphingolipid desaturases differs from that of the membrane-bound non-fusion Delta (12) and Delta (15) desaturases in the pres ence of glutamine instead of histidine. We have used site-directed mutagene sis to determine the importance of glutamine and other residues of the thir d histidine box and created a chimaeric enzyme to determine the ability of the Cyt b(5) fusion domain from the plant sphingolipid desaturase to substi tute for the endogenous domain of the Delta (6) desaturase.