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Reference: Jain S, et al. (2007) Identification of a Novel Lysophospholipid Acyltransferase in Saccharomyces cerevisiae. J Biol Chem 282(42):30562-9

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Abstract

The incorporation of unsaturated acyl chains into phospholipids during de novo synthesis is primarily mediated by the 1-acyl-sn-glycerol-3-phosphate acyltransferase reaction. In S. cerevisiae, Slc1p has been shown to mediate this reaction but distinct activity remains after its removal from the genome. To identify the enzyme that mediates the remaining activity, we performed synthetic genetic array analysis using a slc1 strain. One of the genes identified by the screen, LPT1, was found to encode for an acyltransferase that uses a variety of lysophospholipid species, including 1-acyl-sn-glycerol-3-phosphate. Deletion of LPT1 had a minimal effect on 1-acyl-sn-glycerol-3-phosphate acyltransferase activity but over-expression increased activity 7-fold. Deletion of LPT1 abrogated the esterification of other lysophospholipids and over-expression increased lysophosphatidylcholine acyltransferase activity 7-fold. The majority of this activity co-purified with microsomes. To test the putative role for this enzyme in selectively incorporating unsaturated acyl chains into phospholipids, in vitro, substrate concentration series experiments were performed with the four acyl-CoA species commonly found in yeast. While the saturated palmitoyl-CoA and stearoyl-CoA showed a lower apparent Km, the monounsaturated palmitoleoyl-CoA and oleoyl-CoA showed a higher apparent Vmax. Arachidonyl-CoA, although not abundant in yeast, also had a high apparent Vmax. Pulse-labeling of lpt1 strains showed a 30% reduction in [3H]oleate incorporation into phosphatidylcholine only. Therefore, Lpt1p, a member of the membrane bound o-acyltransferase gene family, seems to work in conjunction with Slc1p to mediate the incorporation of unsaturated acyl-chains into the sn-2 position of phospholipids.

Reference Type
Journal Article
Authors
Jain S, Stanford N, Bhagwat N, Seiler B, Costanzo M, Boone C, Oelkers P
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