The membrane-bound O-acyltransferase Ale1 transfers an acyl moiety to newly synthesized 2-alkyl-sn-glycero-3-phosphocholine in yeast.

To elucidate the mechanism of acyl chain remodeling at the sn-1 position of phosphatidylcholine (PC), we investigated acyl chain introduction using a newly synthesized 1-hydroxy-2-hexadecyl-sn-glycero-3-phosphocholine (HHPC) in Saccharomyces cerevisiae. HHPC is incorporated into yeast cells and converted to a PC species containing acyl residues of 16 or 18 carbons. The efficiency of palmitoleic acid introduction to HHPCin vitro is lower in the reaction with the extract from the deletion mutant of ALE1, which encodes a membrane-bound O-acyltransferase, than in that with extracts from the wild-type strain. In addition, deletion of ALE1 causes reductions in the molecular species containing acyl residues in HHPC. These results reveal that ALE1 is involved in acyl chain transfer to the sn-1 position of HHPC in yeast.

Acyl-chain remodeling of dioctanoyl-phosphatidylcholine in Saccharomyces cerevisiae mutant defective in de novo and salvage phosphatidylcholine synthesis.

A yeast strain, in which endogenous phosphatidylcholine (PC) synthesis is controllable, was constructed by the replacement of the promoter of PCT1, encoding CTP:phosphocholine cytidylyltransferase, with GAL1 promoter in a double deletion mutant of PEM1 and PEM2, encoding phosphatidylethanolamine methyltransferase and phospholipid methyltransferase, respectively. This mutant did not grow in the glucose-containing medium, but the addition of dioctanoyl-phosphatidylcholine (diC8PC) supported its growth. Analyses of the metabolism of (13)C-labeled diC8PC ((methyl-(13)C)3-diC8PC) in this strain using electrospray ionization tandem mass spectrometry revealed that it was converted to PC species containing acyl residues of 16 or 18 carbons at both sn-1 and sn-2 positions. In addition, both acyl residues of (methyl-(13)C)3-diC8PC were replaced with 16:1 acyl chains in the in vitro reaction using the yeast cell extract in the presence of palmitoleoyl-CoA. These results indicate that PC containing short acyl residues was remodeled to those with acyl chains of physiological length in yeast.