PACKTEST for L-Glutamate Quantification: Development of On-site and High-throughput Analytical Kits using L-Glutamate Oxidase Mutant Keita Murai, Hiroki Yamaguchi, Satoru Furuuchi, Kazutoshi Takahashi, Uno Tagami, Moemi Tatsumi, Toshimi Mizukoshi, Hiroshi Miyano, Shuntaro Okauchi, and Masayuki Sugiki
(Received August 21, 2023; Accepted February 27, 2027)
Keywords: L-glutamate, colorimetry, glutamate oxidase, enzyme-based sensing, amino acid analysis
L-glutamate is an umami component found in various foods, and L-glutamate oxidase (LGOX, EC 1.4.3.11) is a FAD-dependent oxidoreductase that catalyzes the oxidative deamination of L-glutamate. A recently reported single-chain LGOX mutant from Streptomyces sp. X-119-6 is a potential material for L-glutamate sensors because this mutant is easier to prepare than the wild type. Herein, we report the development of a simple analytical kit using this LGOX mutant for the on-site quantification of L-glutamate. The kit named PACKTEST was developed using a colorimetric method to estimate the L-glutamate concentration in the range of 1–50 mg/L through visual comparison of the resulting sample color with a standard color sequence. In addition, the PACKTEST kit was combined with a portable photometer for the spectrophotometric quantification of L-glutamate in the range of 0.5–12.0 mg/L. It was used to quantify L-glutamate in commercially available soy sauces, and the results were in good agreement (r = 0.97) with the values obtained using post-column derivatized ion-exchange chromatography. Furthermore, we loaded and dried all the reagents, including enzymes, on a 96-well plate to prepare an enzyme-based sensing device, which showed potential for the high-throughput quantification of L-glutamate.
Corresponding author: Keita Murai and Hiroki Yamaguchi