CYP52A23 from Candida albicans and its Substrate Preference for Fatty Acid Hydroxylation

The pathogenic fungus Candida albicans contains genes encoding five fatty acid hydroxylases belonging to the CYP52 family in its genome. Our previous study reported that CYP52A21 demonstrated typical omega-hydroxylation of lauric acid (Kim D, Cryle MJ, De Voss JJ, Ortiz de Montellano PR (2007) Arch Biochem Biophys 464, 213-220). Functional characterization of CYP52 fatty acid hydroxylases was studied, and their selectivity for hydroxylation was analyzed. Genes for four other CYP52 members (CYP52A22, CYP52A23, CYP52A24, and CYP52C3) from C. albicans were cloned, and their recombinant enzymes were expressed in Escherichia coli. CO-binding spectral analyses showed that the functional P450 holoenzyme was obtained only in CYP52A23, while no holoenzyme peak was observed in the other three CYP52 enzymes. Spectral change of the type II binding was observed in purified CYP52A23 when titrated with fatty acids but none was observed with alkanes. The gas chromatography-mass spectrometry (GC-MS) analysis revealed that CYP52A23 predominantly exhibited omega-hydroxylation activity during the oxidation reaction of fatty acids. Interestingly, it was found that CYP52A23 preferred longer-chain fatty acids (stearic acid and arachidic acid) for its catalytic activities while CYP52A21 preferred mid-chain fatty acids (lauric acid and mystic acid). To analyze the selectivity of fatty acids, hybrid mutagenesis of genes encoding CYP52A21 and CYP52A23 by overlap extension polymerase chain reaction was conducted. Two hybrid mutants containing the N-terminal fragments of CYP52A21 and C-terminal fragments of CYP52A23 displayed higher catalytic activity in palmitic acid and arachidic acid. These results suggested that the C-terminal part of CYP52A23 may be responsible for its preference to longer-chain fatty acids.