Engineering PQQ glucose dehydrogenase with improved substrate specificity. Site-directed mutagenesis studies on the active center of PQQ glucose dehydrogenase.
Site-directed mutagenesis was carried out on the active site of water-soluble PQQ glucose dehydrogenase (PQQGDH-B) to improve its substrate specificity. Amino acid substitution of His168 resulted in a drastic decrease in the enzyme's catalytic activity, consistent with its putative catalytic role. Substitutions were also carried out in neighboring residues, Lys166, Asp167, and Gln169, in an attempt to alter the enzyme's substrate binding site. Lys166 and Gln169 mutants showed only minor changes in substrate specificity profiles. In sharp contrast, mutants of Asp167 showed considerably altered specificity profiles. Of the numerous Asp167 mutants characterized, Asp167Glu showed the best substrate specificity profile, while retaining most of its catalytic activity for glucose and stability. We also investigated the cumulative effect of combining the Asp167Glu substitution with the previously reported Asn452Thr mutation. Interpretation of the effect of the replacement of Asp167 to Glu on the alteration of substrate specificity in relation with the predicted 3D model of PQQGDH-B is also discussed.
Igarashi
Satoshi
S
Department of Biotechnology, Faculty of Technology, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
Hirokawa
Takatsugu
T
Sode
Koji
K
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics*; D004926:Escherichia coli; D005947:Glucose / Q000737:chemistry*; D005948:Glucose Dehydrogenases / Q000737:chemistry* / Q000235:genetics*; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015202:Protein Engineering; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D013379:Substrate Specificity / Q000235:genetics
D005948:Glucose Dehydrogenases; C033955:glucose dehydrogenase (pyrroloquinoline-quinone); D005947:Glucose