The application of L-glutaminase for the synthesis of the immunomodulatory -D-glutamyl-L-tryptophan and the kokumi-imparting -D-glutamyl peptides.

Glutaminase of has been used to synthesize the immunomodulatory -D-glutamyl-L-tryptophan (-D-Glu-L-Trp) and the kokumi-active -D-glutamyl peptides. The optimum yield of -D-Glu-L-Trp was 55.76 mM in corresponding to a minimum yield of by-product (-D-Glu--D-Glu-L-Trp) in the presence of 75 mM D-Gln and 100 mM L-Trp. The glutaminase has a low K values for the donors (D-Gln and L-Gln:5.53 and 0.98 mM), but high ones for the acceptors (L-Trp, L-Phe, L-Met, L-Val and -[D-Glu] -L-Val/L-Phe/L-Met, ranging from 32.51 to 193.05 mM). The highest K value appearing when  = 2 (-[D-Glu] -L-Val/L-Phe/L-Met) suggested the rising difficulty for synthesis when the number of donor increases in the reaction mixtures. The -[D-Glu] -L-Val/L-Phe/L-Met at 5 mM can impart the blank chicken broth an enhancing monthfulness, thickness, and umaminess taste.