Phospholipid:diacylglycerol acyltransferase: An enzyme that catalyzes the acyl-CoA-independent formation of triacylglycerol in yeast and plants

Phospholipid:diacylglycerol acyltransferase: An enzyme that catalyzes the acyl-CoA-independent formation of triacylglycerol in yeast and plants

^*Scandinavian Biotechnology Research (ScanBi) AB, Herman Ehles Väg 2 S-26831 Svalôv, Sweden; ^¶Department of Plant Breeding Research, Swedish University of Agricultural Sciences, Herman Ehles väg 2–4, S-268 31 Svalöv, Sweden; and ^§Department of Plant Biology, Uppsala Genetic Center, Swedish University of Agricultural Sciences, Box 7080, S-750 07 Uppsala, Sweden

Edited by Christopher R. Somerville, Carnegie Institution of Washington, Stanford, CA, and approved March 31, 2000 (received for review February 15, 2000)

Abstract

Triacylglycerol (TAG) is known to be synthesized in a reaction that uses acyl-CoA as acyl donor and diacylglycerol (DAG) as acceptor, and which is catalyzed by the enzyme acyl-CoA:diacylglycerol acyltransferase. We have found that some plants and yeast also have an acyl-CoA-independent mechanism for TAG synthesis, which uses phospholipids as acyl donors and DAG as acceptor. This reaction is catalyzed by an enzyme that we call phospholipid:diacylglycerol acyltransferase, or PDAT. PDAT was characterized in microsomal preparations from three different oil seeds: sunflower, castor bean, and Crepis palaestina. We found that the specificity of the enzyme for the acyl group in the phospholipid varies between these species. Thus, C. palaestina PDAT preferentially incorporates vernoloyl groups into TAG, whereas PDAT from castor bean incorporates both ricinoleoyl and vernoloyl groups. We further found that PDAT activity also is present in yeast microsomes. The substrate specificity of this PDAT depends on the head group of the acyl donor, the acyl group transferred, and the acyl chains of the acceptor DAG. The gene encoding the enzyme was identified. The encoded PDAT protein is related to lecithin:cholesterol acyltransferase, which catalyzes the acyl-CoA-independent synthesis of cholesterol esters. However, budding yeast PDAT and its relatives in fission yeast and Arabidopsis form a distinct branch within this protein superfamily, indicating that a separate PDAT enzyme arose at an early point in evolution.

Footnotes

↵ † A.D. and U.S. contributed equally to this work.
↵ ‡ To whom reprint requests should be addressed. E-mail: anders.dahlqvist{at}vf.slu.se.
This paper was submitted directly (Track II) to the PNAS office.
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.120067297.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.120067297
Abbreviations:

TAG,

triacylglycerol;

DAGAT,

diacylglycerol acyltransferase;

DAG,

diacylglycerol;

ACAT,

acyl-CoA:cholesterol acyltransferase;

PDAT,

phospholipid:diacylglycerol acyltransferase;

LCAT,

lecithin:cholesterol acyltransferase;

PE,

phosphatidylethanolamine;

PC,

phosphatidylcholine