Cloning of a Coconut Endosperm cDNA Encoding a 1-Acyl-sn-Glycerol-3-Phosphate Acyltransferase That Accepts Medium-Chain-Length Substrates

Abstract

The fatty acyl groups found in membrane phospholipids of higher plants are predominantly 16 or 18 carbons in length. However, the seed TAGs of many plants contain large amounts of fatty acyl groups different from those found in the phospholipids, suggesting that mechanisms exist for partitioning of specific fatty acids into the TAG fraction. Seed storage TAGs are synthesized in the ER from acyl-COA and glycerol-3-P in a series of reactions termed the Kennedy pathway (reviewed by Stymne and Stobart, 1987;Frentzen, 1993). The first step of this pathway is the acylation of the sn-1 position of glycerol-3-P (catalyzed by glycerol-3-P acyltransferase) to form 1-acyl sn-glycerol-3-P, also termed LPA. The sn-2 position of LPA is subsequently acylated to yield PA in a reaction catalyzed by 1-acyl sn-glycerol-3-P acyltransferase (EC 2.3.1.51). This enzyme is more commonly known as LPAAT. Formation of TAG is completed by dephosphorylation of PA to produce diacylglycerol and the transfer of a third acyl group to the sn-3 position of the glycerol backbone by diacylglycerol acyltransferase. Synthesis of precursors of membrane phospholipids can also occur via a similar set of enzymatic steps

The Significance of C16 Fatty Acids in the sn-2 Positions of Glycerolipids in the Photosynthetic Growth of Synechocystis sp. PCC6803

“…Another type of endoplasmic reticulumlocated LPAAT is involved in triacylglycerol synthesis and uses unusual fatty acids such as 12:0 or 22:1. These LPAAT are seed-specific LPAAT and have 63 amino acid residues between the conserved motif signatures (Brown et al, 1995;Knutzon et al, 1995;Lassner et al, 1995). Because sll1752 has a distance of 64 amino acid residues between the HXXXXD and the XXXXXXG signatures, this number is most similar to that of seedspecific LPAATs.…”

Characterization of a Human Lysophosphatidic Acid Acyltransferase That Is Encoded by a Gene Located in the Class III Region of the Human Major Histocompatibility Complex

“…2) such as bacteria (Hemophilus influenzae (30.4% identity) (23), Salmonella typhimurium (28.1% identity) (24), Escherichia coli (27.7% identity) (25), Neisseria gonorrhoeae (24.9% identity), and Neisseria meningitidis (24.0% identity) (26)); yeast (Saccharomyces cerevisiae (30.9% identity) (27)); and plant (Limnantes alba (28.4% identity) (28) and Cocos nucifera (23.6% identity) (29) (Fig. 2a)).…”

Human Lysophosphatidic Acid Acyltransferase

“…Genomic DNA and cDNA Cloning-A TBLASTN search of the GenBank TM dbest data base using the coconut LPAAT sequence (25) identified two human ESTs deposited by the WashU-Merck EST project with accession numbers H39628 and H44282. Based upon the EST sequences, two oligonucleotide primers (forward: 5Ј-GGGCCTCATCA-TGTACCTCGGGGGCG-3Ј; reverse: 5Ј-CTGCCCTCCCCCAGGTC-3Ј) were designed and used in a polymerase chain reaction (PCR) to obtain a fragment of the LPAAT homologue cDNA from a human macrophage cDNA library (26).…”

“…In plants, storage triacylglycerols are synthesized via a four-step pathway that involves acylation of glycerol 3-phosphate at the sn-1 position to form LPA, acylation of LPA by LPAAT, and then conversion of the PA to diacylglycerol by PA phosphatase followed by sn-3 acylation to form triacylglycerol (21). Interest in this metabolic pathway from the perspective of understanding and manipulating plant oil production has resulted in the cloning of several plant cDNAs that encode enzymes with LPAAT activity (22)(23)(24)(25). Interestingly, these cDNAs have extensive * The costs of publication of this article were defrayed in part by the payment of page charges.…”