Characterization of two Arabidopsis thaliana acyltransferases with preference for lysophosphatidylethanolamine.
BACKGROUND
Two previously uncharacterized Arabidopsis genes that encode proteins with acyltransferase PlsC regions were selected for study based on their sequence similarity to a recently identified lung lysophosphatidylcholine acyltransferase (LPCAT). To identify their substrate specificity and biochemical properties, the two Arabidopsis acyltransferases, designated AtLPEAT1, (At1g80950), and AtLPEAT2 (At2g45670) were expressed in yeast knockout lines ale1 and slc1 that are deficient in microsomal lysophosphatidyl acyltransferase activities.


RESULTS
Expression of AtLPEAT1 in the yeast knockout ale1 background exhibited strong acylation activity of lysophosphatidylethanolamine (LPE) and lysophosphatidate (LPA) with lower activity on lysophosphatidylcholine (LPC) and lysophosphatidylserine (LPS). AtLPEAT2 had specificities in the order of LPE > LPC > LPS and had no or very low activity with LPA. Both acyltransferases preferred 18:1-LPE over 16:0-LPE as acceptor and preferred palmitoyl-CoA as acyl donor in combination with 18:1-LPE. Both acyltransferases showed no or minor responses to Ca2+, despite the presence of a calcium binding EF-hand region in AtLPEAT2. AtLPEAT1 was more active at basic pH while AtLPEAT2 was equally active between pH 6.0 - 9.0.


CONCLUSIONS
This study represents the first description of plant acyltransferases with a preference for LPE. In conclusion it is suggested that the two AtLPEATs, with their different biochemical and expression properties, have different roles in membrane metabolism/homoeostasis.
Stålberg
Kjell
K
Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden. kjell.stalberg@vbsg.slu.se
Ståhl
Ulf
U
Stymne
Sten
S
Ohlrogge
John
J
D000215:Acylation; D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D008246:Lysophospholipids / Q000378:metabolism*; D008969:Molecular Sequence Data; D013379:Substrate Specificity
D029681:Arabidopsis Proteins; D018076:DNA, Complementary; D008246:Lysophospholipids; C008301:lysophosphatidylethanolamine; D000217:Acyltransferases