Purification and Characterization of a Novel 5-Oxoprolinase (without ATP-Hydrolyzing Activity) from Alcaligenes faecalis N-38A

requirements for metal ions such as Mg 21 and K 1 . The optimal pH for the decyclization was 7.4. The reaction was reversible. The equilibrium constant of the reaction, Keq 5 [L-glutamate]/[L-pyroglutamate], was evaluated to be approximately 0.035, which indicates that the reaction tends to form L-pyroglutamate. The aminoterminal amino acid sequence of the enzyme was H-Glu-Pro-Arg-Leu-Asp-Thr-Ser-Gln-Leu-Tyr-Ala-Asp-ValHis-Phe-. No protein with a similar sequence was found in the DNASIS database. Based on these data, it was strongly suggested that the enzyme described here is a novel type of 5-oxoprolinase. L-Monosodium glutamate is used as a flavor enhancer in food. It is recognized in food technology that the concentration of glutamate in a given product is very important for its quality when proteins are hydrolyzed enzymatically to produce seasonings such as soy sauce.