Improvement of the bitter taste of amino acids through the transpeptidation reaction of bacterial gamma-glutamyltranspeptidase.
The tastes of several bitter amino acids and their gamma-glutamyl derivatives were compared. The bitterness of Phe, Val, Leu, and His was reduced, sourness was produced, and preferences were increased by gamma-glutamylization. Because the effect of gamma-glutamylization of bitter amino acids was most obvious for Phe, which is an atypical bitter amino acid, an enzymatic method for the synthesis of gamma-glutamylphenylalanine (gamma-Glu-Phe) involving bacterial gamma-glutamyltranspeptidase was developed. The optimum reaction conditions were 200 mM Gln, 200 mM Phe, and 0.5 unit/mL GGT, pH 10.4. After 1.5-h of incubation at 37 degrees C, 140 mM gamma-Glu-Phe was obtained, the yield being 70%. gamma-Glu-Phe was purified on a Dowex 1x8 column and then identified by NMR.
Suzuki
Hideyuki
H
Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan. hideyuki@lif.kyoto-u.ac.jp
Kajimoto
Yoko
Y
Kumagai
Hidehiko
H
D000596:Amino Acids / Q000032:analysis / Q000737:chemistry*; D004151:Dipeptides / Q000138:chemical synthesis / Q000302:isolation & purification; D004926:Escherichia coli / Q000201:enzymology; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D013649:Taste; D005723:gamma-Glutamyltransferase / Q000378:metabolism*
D000596:Amino Acids; D004151:Dipeptides; C020621:gamma-glutamylphenylalanine; D005723:gamma-Glutamyltransferase