Journal of Lipid Research, Vol 29, 9-14, Copyright © 1988 by Lipid Research, Inc.
Phosphatidylcholine synthesis in yeast
J Chin and K Bloch
James Bryant Conant Laboratories, Harvard University, Cambridge, MA 02138.
The two pathways for the biosynthesis of phosphatidylcholine, by way of
phosphocholine and by methylation of phosphatidylethanolamine, in wild-
type yeast (Saccharomyces cerevisiae) and in the yeast mutant GL7 have been
compared. The mutant requires for growth a sterol, unsaturated fatty acids,
and methionine. The uptake of labeled choline or labeled methionine and
their conversion to phosphatidylcholine were determined in both cell types.
The activities of the major enzymes for both pathways were assayed in
vitro. We find that the methylation pathway is predominant in both
wild-type and mutant cells though the overall activity of the choline
pathway is lower in the yeast mutant. The methionine analogue ethionine
inhibits the growth of the mutant more strongly than growth of wild-type
yeast. Ethionine, while a powerful inhibitor of phosphatidylcholine
synthesis by methylation, stimulates the choline pathway in both cell
types.
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