Phosphatidylserine synthase plays a critical role in the utilization of n-alkanes in the yeast Yarrowia lipolytica

The yeast Yarrowia lipolytica can assimilate n-alkane as a carbon and energy source. To elucidate the significance of phosphatidylserine (PS) in the utilization of n-alkane in Y. lipolytica, we investigated the role of the Y. lipolytica ortholog (PSS1) of Saccharomyces cerevisiae PSS1/CHO1, which encodes a PS synthase. The PSS1 deletion mutant (pss1 Delta) of Y. lipolytica could not grow on minimal medium in the absence of ethanolamine and choline but grew when either ethanolamine or choline was supplied to synthesize phosphatidylethanolamine and phosphatidylcholine. The pss1 Delta strain exhibited severe growth defects on media containing n-alkanes even in the presence of ethanolamine and choline. In the pss1 Delta strain, the transcription of ALK1, which encodes a primary cytochrome P450 that catalyses the hydroxylation of n-alkanes in the endoplasmic reticulum, was upregulated by n-alkane as in the wild-type strain. However, the production of functional P450 was not detected, as indicated by the absence of reduced CO-difference spectra in the pss1 Delta strain. PS was undetectable in the lipid extracts of the pss1 Delta strain. These results underscore the critical role of PSS1 in the biosynthesis of PS, which is essential for the production of functional P450 enzymes involved in n-alkane hydroxylation in Y. lipolytica. Phosphatidylserine synthase is critical for the utilization of n-alkane and the production of functional P450 involved in the hydroxylation of n-alkane in Yarrowia lipolytica.