Characterization of Acid Phosphatase (AphC) from the Miso Koji Mold, Aspergillus oryzae KBN630: AphC is Mainly Responsible for Both Acid Phosphatase Activity and 5′-IMP Dephosphorylation Activity in Soybean-Koji Culture

抄録

Single disruption of seven acid phosphatase genes (aphB-H) demonstrated that the aphC gene is mainly responsible for acid phosphatase production in the soybean-koji culture of the miso koji mold, A. oryzae KBN630. None of the single disruptions of aphB-H affected growth in the culture. Both the acid phosphatase activity and 5′-IMP dephosphorylation activity of the aphC disruptant decreased by 95% compared to the wild-type strain. Utilizing the promoter of the A. oryzae taaG2 gene, AphC was successfully overproduced in A. oryzae and secreted into liquid culture medium. The purified AphC had a molecular mass of 69.0 kDa, a pH optimum of 4.5, and a temperature optimum of 50°C. AphC exhibited high dephosphorylation activity towards the umami flavor enhancers, 5′-IMP and 5'-GMP, supporting the idea that AphC is involved in degradation of disodium 5′-ribonucleotides supplemented in miso products.