Assay of NAT Activity

In animal tissues, N-acyltransferase (NAT) catalyzes the first reaction in the biosynthetic pathway of bioactive N-acylethanolamines, in which an acyl chain is transferred from the sn-1 position of the donor phospholipid, such as phosphatidylcholine, to the amino group of phosphatidylethanolamine, resulting in the formation of N-acylphosphatidylethanolamine. NAT has long been known to be stimulated by Ca2+ and hence referred to as Ca2+-dependent NAT. Later, this enzyme was identified as cPLA2ε (also referred to as PLA2G4E). On the other hand, members of the phospholipase A/acyltransferase (PLAAT) family (also known as HRAS-like suppressor family) show Ca2+-independent NAT activity. In this chapter, we describe (1) partial purification of Ca2+-dependent NAT from rat brain, (2) purification of recombinant cPLA2ε and PLAAT-2, and (3) NAT assay using radiolabeled substrate.