Molecular Characterization of a Phospholipase D Generating Anandamide and Its Congeners

TLDR

Anandamide and related N‑acylethanolamines are endogenous ligands of cannabinoid and vanilloid receptors, produced from N‑acyl‑phosphatidylethanolamines by a phospholipase D‑type enzyme in animal tissues. The enzyme was purified from rat heart and its complementary DNAs were cloned from mouse, rat, and human using internal peptide sequences. The 393–396‑residue enzyme, a zinc metallohydrolase of the β‑lactamase fold, catalyzes anandamide and other N‑acylethanolamines from their phosphatidylethanolamine precursors, is inactive on phosphatidylcholine and phosphatidylethanolamine, and is widely expressed—especially in brain, kidney, and testis—confirming its role in generating these lipid signaling molecules.

Abstract

Anandamide (<i>N</i>-arachidonoylethanolamine) is known to be an endogenous ligand of cannabinoid and vanilloid receptors. Its congeners (collectively referred to as <i>N</i>-acylethanolamines) also show a variety of biological activities. These compounds are principally formed from their corresponding <i>N</i>-acyl-phosphatidylethanolamines by a phosphodiesterase of the phospholipase D-type in animal tissues. We purified the enzyme from rat heart, and by the use of the sequences of its internal peptides cloned its complementary DNAs from mouse, rat, and human. The deduced amino acid sequences were composed of 393–396 residues, and showed that the enzyme has no homology with the known phospholipase D enzymes but is classified as a member of the zinc metallohydrolase family of the β-lactamase fold. As was overexpressed in COS-7 cells, the recombinant enzyme generated anandamide and other <i>N</i>-acylethanolamines from their corresponding <i>N</i>-acyl-phosphatidylethanolamines at comparable rates. In contrast, the enzyme was inactive with phosphatidylcholine and phosphatidylethanolamine. Assays of the enzyme activity and the messenger RNA and protein levels revealed its wide distribution in murine organs with higher contents in the brain, kidney, and testis. These results confirm that a specific phospholipase D is responsible for the generation of <i>N</i>-acylethanolamines including anandamide, strongly suggesting the physiological importance of lipid molecules of this class.