Abstract
The mechanism of formation of 5'-IMP during soaking of Katsuobushi in cold water in preparing Mizudashijiru, i. e., uncooked soup stock was studied. The enzyme from the molding surface of Hongarebushi, which catalyzes formation of 5'-IMP from 5'-AMP, was purified through ammonium sulfate fractionation followed by DEAE-cellulose column chromatography and properties of the purified enzyme were examined.
The enzyme had pH optimum of 5. 6, which was almost the same as the pH of Mizudashijiru. This result indicated that the pH condition of Mizudashijiru was good for activity of this enzyme. The enzyme was not affected by Na+, K+, Mg2+ or Ca2+. It had 18% activity at 5°C compared with its maximal activity at the optimum temperature, and was stable at 5°C for 5 days. From these results, we assumed that this enzyme acts weakly during soaking of Hongarebushi in cold water in preparing Mizudashijiru.
