Occurrence of N-methyl-L-aspartate in bivalves and its distribution compared with that of N-methyl-D-aspartate and D,L-aspartate

The presence of N-methyl-L-aspartate (NMLA) was demonstrated in bivalves, C orbicula sandai and Tapes japonica. To our knowledge, this is the first rep ort on the occurrence of NMLA in animal tissues. NMLA in bivalve tissues wa s identified according to the following findings; (a) its derivatives with (+)- and (-)- 1-(9-fluorenyl)ethyl chloroformate (FLEC behaved identically with those of authentic NMLA, respectively, on high-performance liquid chro matography (HPLC, (b) its derivatives with (+)- and (-)- FLEC behaved ident ically with (-)- and (+)-FLEC derivatives of authentic N-methyl-D-aspartate (NMDA), respectively, on HPLC and (c) its behavior on thin-layer chromatog raphy was the same as those of authentic NMLA. We also describe the distrib ution of NMDA, and D- and L-aspartate, to which N-methylaspartate enantiome rs are structurally related. NMDA was more widely dirtributed than NMLA in bivalves. These bivalves containing NMLA showed lower D-aspartate contents and D/(D + L) ratios of aspartate, than the bivalves containing NMDA. (C) 2 001 Elsevier Science Inc. All rights reserved.