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Structural elements responsible for the glucosidic linkage‐selectivity of a glycoside hydrolase family 13 exo‐glucosidase
Author(s) -
Saburi Wataru,
Rachi-Otsuka Hiroaki,
Hondoh Hironori,
Okuyama Masayuki,
Mori Haruhide,
Kimura Atsuo
Publication year - 2015
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2015.02.023
Subject(s) - isomaltose , maltose , glycoside hydrolase , chemistry , hydrolase , glucosidases , selectivity , biochemistry , glucosyltransferases , enzyme , stereochemistry , catalysis
Glycoside hydrolase family 13 contains exo‐glucosidases specific for α‐(1 → 4)‐ and α‐(1 → 6)‐linkages including α‐glucosidase, oligo‐1,6‐glucosidase, and dextran glucosidase. The α‐(1 → 6)‐linkage selectivity of Streptococcus mutans dextran glucosidase was altered to α‐(1 → 4)‐linkage selectivity through site‐directed mutations at Val195, Lys275, and Glu371. V195A showed 1300‐fold higher k cat / K m for maltose than wild‐type, but its k cat / K m for isomaltose remained 2‐fold higher than for maltose. K275A and E371A combined with V195A mutation only decreased isomaltase activity. V195A/K275A, V195A/E371A, and V195A/K275A/E371A showed 27‐, 26‐, and 73‐fold higher k cat / K m for maltose than for isomaltose, respectively. Consequently, the three residues are structural elements for recognition of the α‐(1 → 6)‐glucosidic linkage.