A simultaneous assay method for L-glutamate and L-pyroglutamate contents in soy sauce using a 5-oxoprolinase (without ATP hydrolyzing activity)

L-Glutamine and L-glutamate, which are important flavor components in soy s auce, are converted to L-pyroglutamate during brewing. Therefore, it is nec essary that the L-glutamate and L-pyroglutamate contents can be measured ac curately. We developed a simultaneous assay method for L-glutamate and L-py roglutamate by using 5-oxoprolinase (without ATP hydrolyzing activity) and glutamate oxidase. By this method, the L-pyroglutamate could be measured ac curately in a range of 0.05 to 1.0 mM in the presence of 1.0 mM L-glutamate . This system is effective for process and quality controls.