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The role of group bulkiness in the catalytic activity of psychrophile cold‐active protein tyrosine phosphatase
Author(s) -
Tsuruta Hiroki,
Mikami Bunzo,
Yamamoto Chiaki,
Yamagata Hiroshi
Publication year - 2008
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2008.06575.x
Subject(s) - thermostability , psychrophile , active site , chemistry , enzyme , hydrolase , protein tyrosine phosphatase , phosphatase , tyrosine , biochemistry
The cold‐active protein tyrosine phosphatase found in psychrophilic Shewanella species exhibits high catalytic efficiency at low temperatures as well as low thermostability, both of which are characteristics shared by many cold‐active enzymes. The structure of cold‐active protein tyrosine phosphatase is notable for the presence of three hydrophobic sites (termed the CA, Zn‐1 and Zn‐2 sites) behind the loop structures comprising the catalytic region. To identify the structural components responsible for specific enzyme characteristics, we determined the structure of wild‐type cold‐active protein tyrosine phosphatase at high resolution (1.1 Å) and measured the catalytic efficiencies of enzymes containing mutations in the three hydrophobic sites. The bulkiness of the amino acid side chains in the core region of the Zn‐1 site strongly affects the thermostability and the catalytic efficiency at low temperatures. The mutant enzyme I115M possessed a higher k cat at low temperatures. Elucidation of the crystal structure of I115M at a resolution of 1.5 Å revealed that the loop structures involved in retaining the nucleophilic group and the acid catalyst are more flexible than in the wild‐type enzyme.