Food Science and Technology Research
Online ISSN : 1881-3984
Print ISSN : 1344-6606
ISSN-L : 1344-6606
Original papers
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
Shoko Yoshino-Yasuda Emi NakamuraNatsuko OnoOsamu HasegawaYoshimi IgaYohei ShiraishiYutaka WaguKazuhiro SugimotoTohru SuzukiTatsuya SugimotoKen-Ichi KusumotoMasashi KatoNoriyuki Kitamoto
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2014 Volume 20 Issue 2 Pages 367-374

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Abstract

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.

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© 2014 by Japanese Society for Food Science and Technology
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