Identification and characterization of a novel delta12-fatty acid desaturase gene from Rhizopus arrhizus.

Based on the sequence information of Delta12-fatty acid desaturase genes (from Mucor circinelloides, Mortierella alpina, Mucor rouxii and Aspergillus nidulans), which were involved in the conversion from C18:1 to C18:2, a cDNA sequence putatively encoding a Delta12-fatty acid desaturase was isolated from Rhizopus arrhizus using the combination of reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) methods. Sequence analysis indicated that it had an open reading frame (ORF) of 1170 bp, coding for 389 amino acid residues of 45 kDa, pI of the deduced protein was 7.01. The deduced amino acid sequence of this cloned cDNA showed high identity to those filamentous fungal Delta12-desaturases mentioned above, including three conserved histidine-rich motifs and two hydrophobic domains. Functional identification was done heterologously in Saccharomyces cerevisiae strain INVScl. The result demonstrated that the deduced amino acid sequence exhibited Delta12-fatty acid desaturase activity, suggesting that this gene encoded for a membrane-bound desaturase, Delta12-fatty acid desaturase.