Screening of Salt Taste Enhancing Dipeptides Based on a New Strategy Using _L-Amino Acid Ligase

Abstract

Many dipeptides have unique physiological functions such as antihypertensive effects and taste enhancing effects. In this study, we focused on the taste of dipeptides and conducted screening for dipeptides as salt taste enhancers. Dipeptides were synthesized using TabS, an L-amino acid ligase (Lal) from Pseudomonas syringae NBRC14081. Six kinds of amino acids, which were easily released by the hydrolysis of proteins or peptides, reacted with 20 proteogenic amino acids, and the reaction mixtures were evaluated using sensory evaluation. In the first screening, the reaction mixture or L-Leu-L-Ser, a known salt taste enhancing dipeptide, was added to a salt solution containing ATP and panelists judged the salt taste intensities. In the second screening, the reaction mixture or residual substrate amino acids was added to a salt solution containing ATP and subjected to sensory evaluation. LMet-Gly was identified as a candidate salt taste enhancer. In addition to sensory evaluation, the salt taste enhancing effect of L-Met-Gly was evaluated using a taste sensor. Taste sensor analysis showed that L-Met-Gly had a salt taste enhancing effect, and the relative sensor response for L-Met-Gly was equal to or higher than that for L-Leu-L-Ser. This is the first report that L-Met-Gly is a salt taste enhancing dipeptide. Furthermore, we propose that the screening method using reaction mixtures of Lal is applicable for the taste evaluation of other dipeptides.

Alteration of the substrate specificity of l-amino acid ligase and selective synthesis of Met-Gly as a salt taste enhancer

“…19) We have used to synthesize dipeptides in a search for salt-tasteenhancing dipeptides. 13) We previously reported that Met-Gly and Met-Met are produced by TabS, with the amount of Met-Met was exceeding that of Met-Gly. 13) If Met-Gly is to be supplied by Lal efficiently, it is necessary to synthesize it selectively without byproducts.…”

“…13) The dipeptides we used to perform our screening were synthesized by L-amino acid ligase (Lal, EC 6.3.2.28). Lal, a member of the ATP-dependent carboxylate-amine/thiol ligase superfamily, 14) is a microbial enzyme that catalyzes dipeptide synthesis from unprotected L-amino acids by hydrolysis of ATP to ADP.…”

Development of a Sensor with a Lipid/Polymer Membrane Comprising Na+ Ionophores to Evaluate the Saltiness Enhancement Effect

“…The saltiness enhancement effect is the effect whereby saltiness is enhanced by adding specific substances to salt (sodium chloride). Various substances have been reported to be saltiness-enhancing substances contributing to this effect: amino acids such as asparagine and glutamine; branched-chain amino acids (BCAAs) such as valine, leucine and isoleucine, dipeptides such as methionylglycine, sour substances such as tartaric acid and citric acid, protein hydrolysates including amino acids and dipeptides, and so forth [3,4,5,6,7,8,9,10]. In addition, it has been revealed that the flavor of bacon or soy sauce, and spicy substances such as spiranthol, can also enhance the saltiness of food [11,12,13,14,15].…”