Yeast Delta 12 fatty acid desaturase: gene cloning, expression, and function.

In an effort to elucidate the molecular mechanisms of fatty acid desaturation in yeast, a complete gene encoding Delta 12 fatty acid desaturase of Saccharomyces kluyveri was cloned. The open reading frame of this gene (named Sk-FAD2) consists of 1,251 bp, encoding 416 amino acids. The deduced Sk-FAD2 protein had 37-55% identity with those from other filamentous fungi. Unlike the genes of these other fungi, S. cerevisiae expressing Sk-FAD2 was found to be capable of synthesizing the dienoic fatty acid hexadecadienoic acid as well as linoleic acid. Moreover, the Sk-FAD2-disrupted strain of S. kluyveri was unable to produce polyunsaturated fatty acids. These results suggested that Sk-FAD2 protein is a unique Delta 12 fatty acid desaturase in S. kluyveri. Analysis of transcriptional expression revealed that Sk-FAD2 was not repressed by exogenous unsaturated fatty acids but responded to low-temperature stress.