Microplate-based fluorometric methods for the enzymatic determination of L-glutamate: application in measuring L-glutamate in food samples

This report describes two microplate-based fluorometric methods for measuring L-glutamate in a 96-well microplate assay. These two methods combine the advantageous enzymatic recycling and the highly sensitive fluorogenic indicators of Amplex Red and resazurin. In comparison with the existing assay, the Amplex Red-based assay is over 500-fold more sensitive with the detection limit of 0.5 pmol per well, and the resazurin-based assay is over 100-fold more sensitive with the detection limit 2.0 pmol per well. Both methods have been found to reliably detect MSG levels in foodstuffs. With their high sensitivity and the superior spectral properties of the indicators used, the Amplex Red- and resazurin-based methods should be useful for the determination of L-glutamate levels in foodstuffs, as well as in other biological and clinical samples. (C)1999 Elsevier Science B.V. All rights reserved.