Further characterization of A ' - sphingolipid desaturases from higher plants

The consensus sequence of the third histidine box of a range of A,, A6, An and sphingolipid desaturases differs from that of the membrane-bound non-fusion A'' and A15 desaturases in the presence of glutamine instead of histidine. We have used site-directed mutagenesis to determine the importance of glutamine and other residues of the third histidine box and created a chimaeric enzyme to determine the ability of the Cyt 6, fusion domain from the plant sphingolipid desaturase to substitute for the endogenous domain of the A, desaturase.