Delta(6)-Desaturase of Mucor rouxii with high similarity to plant Delta(6)-desaturase and its heterologous expression in Saccharomyces cerevisiae

Gamma-linolenic acid (GLA, gamma -C18:3) is an essential fatty acid that pl ays a vital role in biological structures and cellular functions. Based on available sequence information and using polymerase chain reaction (PCR) te chnique, we cloned from the fungus Mucor rouxii the entire coding sequence of a Delta (6)-desaturase enzyme, which is responsible for the transformati on of linoleic acid into GLA. The deduced amino acid sequence of M. rouxii gene showed the highest homology with the plant Delta6-desaturase. It compr ises the characteristics of membrane-bound desaturases, including histidine -rich motifs and hydrophobic regions. A cytochrome b(5)-like domain was obs erved at the N-terminus. In addition to three conserved histidine-rich moti fs, we found an additional histidine-rich motif, HKHHSH, downstream of the cytochrome b(5)-like domain, which is not present in previously cloned Delt a (6)-desaturase genes. Heterologous expression of the M. rouxii cDNA in Sa ccharomyces cerevisiae resulted in the synthesis and accumulation of GLA. ( C) 2000 Academic Press.