Improved substrate specificity and dynamic range for glucose measurement of Escherichia coli PQQ glucose dehydrogenase by site directed mutagenesis |
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Authors: | K Sode K Kojima |
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Institution: | (1) Department of Biotechnology, Faculty of Technology, Tokyo University of Agriculture and Technology, 2-24-16 Nakamachi, Koganei Tokyo, 184, Japan |
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Abstract: | Site directed mutagenesis study was carried out with Escherichia coli pyrroloquinoline quinone glucose dehydroge-nase (PQQGDH) by substitution of His775 with either Asn (H775N) or Asp (H775D). The mutated PQQGDHs had different substrate specificity and catalytic activity from the wild type PQQGDH. The K values of H775N for 2-deoxy-D-glucose and for D-allose increased for 10-fold. The K values for both D-mannose and D-galactose were estimated much higher than 100 mM. H775D also showed the increase in K values toward saccharides. As a result, these mutants possessed narrower substrate specificity than wild type E. coli PQQGDH. H775D showed the increase in K value for glucose versus wild type PQQGDH (25-fold), therefore H775D is suitable for the direct measurement of blood glucose. The role of His775 in E. coli. PQQGDH is also discussed. |
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