The putative N ‐acyl PE synthase from Arabidopsis thaliana is a lyso‐glycerophospholipid acyltransferase

N ‐acylphosphatidylethanolamine ( N ‐acyl PE) is a minor membrane phospholipid found in plants, animals, and Escherichia coli . Currently, its biosynthesis and function in E. coli are not fully understood. Recently, At1g78690p, a gene isolated from Arabidopsis thaliana , has been reported to encode an N ‐acyltransferase that transfers an acyl chain from acyl‐CoA to the headgroup of PE, making N ‐acyl PE. Our investigation suggests that At1g78690p is not a PE‐dependent N ‐acyltransferase, but is instead a lyso‐glycerophospholipid (lyso‐GPL) acyltransferase. We overexpressed At1g78690p in E. coli , extracted the cellular lipids, and identified the accumulating phospholipid. Electrospray ionization quadrupole time‐of‐flight mass spectrometry analysis yields [M‐H] − ions corresponding by exact mass to acylphosphatidylglycerol (acyl PG) rather than N ‐acyl PE. Collision‐induced decomposition mass spectrometry (MS/MS) corroborates this finding. In addition, in vitro enzyme assays of crude extracts from cells overexpressing At1g78690p using radiolabeled substrates show that At1g78690p acylates lyso‐PE and lyso‐PG, but not PE or PG, in an acyl‐CoA‐dependent manner. We believe that At1g78690p from A. thaliana is a lyso‐GPL acyltransferase, rather than an N ‐acyl PE synthase. We are in the process of determining which position of the lyso‐GPL substrates At1g78690p acylates.