Liquid chromatography-electrospray ionization-tandem mass spectrometric assay for d-aspartate N-methyltransferase activity in ark shells

Abstract

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 Nα-(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. Abbreviations: NMDA: N-methyl-d-aspartate; NMLA: N-methyl-l-aspartate; NMDG: N-methyl-d-glutamate; NMLG: N-methyl-l-glutamate; NMA: N-methylaspartate; NMG: N-methylglutamate; HPLC: high-performance liquid chromatography; SAM: S-adenosyl-l-methionine; OPA: o-phthalaldehyde; LC-ESI-MS/MS: liquid chromatography-electrospray ionization-tandem mass spectrometry; FDLA: Nα-(5-fluoro-2,4-dinitrophenyl)-l-leucinamide; FDAA: Nα-(5-fluoro-2,4-dinitrophenyl)-l-alaninamide; ESI: electrospray ionization; LC-ESI-MS: liquid chromatography-electrospray ionization-mass spectrometry; MS/MS: tandem mass spectrometry