The P-OLE1 gene of Pichia angusta encodes a delta 9-fatty acid desaturase and complements the ole1 mutation of Saccharomyces cerevisiae.

Three PCR-amplified DNA fragments hybridizing with the OLE1 gene encoding delta 9-fatty acid desaturase of Saccharomyces cerevisiae were obtained using, respectively, genomic DNAs of one strain each of Kluyveromyces thermotolerans, Pichia angusta and Yarrowia lipolytica as templates. A gene designated P-OLE1 was cloned from the above fragment of P. angusta and sequenced. An open reading frame of P-OLE1 encodes a 49.6-kDa protein consisting of 451 amino acid residues, which shows high identity (62%) and similarity (89%) to that deduced from the OLE1 nucleotide sequence. Expression of P-OLE1 driven by the S. cerevisiae GAP promoter or its own promoter complemented the ole1 mutation of S.cerevisiae. Transcription of P-OLE1 in the native host was suggested to be partially repressed by oleic acid in the medium, as was that of OLE1 in S. cerevisiae and a similar gene in Y. lipolytica, but that of a similar gene in K. thermotolerans was not.