Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometric Assay For D-Aspartate N-Methyltransferase Activity In Ark Shells

A liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method for the separation and quantification of the enantiomers of N-methylaspartate and N-methylglutamate, after derivatization with N-alpha-(5-fluoro-2,4-dinitrophenyl)-L-leucinamide was established. The time required for the LC-ESI-MS/MS analysis was within 20 min and the detection limit was approximately 10 fmol per injection, demonstrating that this method can be used for the rapid determination of D-aspartate N-methyltransferase activity in the ark shell clam Scapharca broughtonii.