Phospholipid Biosynthesis in Growing and Non-growing Conditions in Candida albicans

The major membrane phospholipids of Candida albicans (C. albicans) are phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (Pi), and phosphatidylserine (PS). In Saccharomyces cerevisiae (S. cerevisiae), the most abundant component PC is considered to be synthesized mainly by two pathways; stepwise methylation pathway of PE produced from PS by decarboxylation (de novo pathway) and diacylglycerol (DG)/CDP-choline pathway. However, relatively little information is available regarding the phospholipid biosynthesis in C. albicans. In order to clarify the phospholipid metabolism of this organism, we have investigated the ³² Pi incorporation into different phospholipids by continuous and pulse-labeling in cells grown in the synthetic medium (SM) and yeast extractproteose peptone-dextrose (YPD) medium. The continuous labeling with ³²Pi in YPD medium showed that the decreases in radioactivity in acidic phospholipids (PA, PI and PS) were followed by the great increase in PC, suggesting the existence of de novo pathway. In SM cultured cells showing no growth, PS and PI were heavily labeled, while PC was much less labeled. By the switch from SM to YPD, the rapid increase in ³²P-labeled PC occurred at the expense of PI and PS, suggesting that the principal PC synthesis for membrane biogenesis is via the de novo pathway in C. albicans.