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The cold-active protein tyrosine phosphatase found in psychrophilicShewa-nellaspecies exhibits high catalytic efficiency at low temperatures as well as low thermostability, both of which are characteristics shared by many cold-active enzymes. | ỊFEBS Journal The role of group bulkiness in the catalytic activity of psychrophile cold-active protein tyrosine phosphatase Hiroki Tsuruta1 Bunzo Mikami2 Chiaki Yamamoto3 and Hiroshi Yamagata3 1 Office of Collaborative Research and Technology Development Kobe University Hyogo Prefecture Japan 2 Laboratory of Applied StructuralBiology Division of Applied Life Sciences Graduate Schoolof Agriculture Kyoto University Kyoto Prefecture Japan 3 Laboratory of BiologicalChemistry Department of BiofunctionalChemistry Graduate Schoolof AgriculturalScience Kobe University Hyogo Prefecture Japan Keywords catalytic efficiency cold-active protein tyrosine phosphatase crystal structure group bulkiness psychrophile Correspondence H. Tsuruta Office of Collaborative Research and Technology Development Kobe University Rokkodai 1-1 Nada Kobe Hyogo Prefecture 657-8501 Japan Fax 81 78 803 5947 Tel 81 78 803 5946 E-mail tsuruta@kobe-u.ac.jp Database The atomic coordinates of the wild-type and the I115M mutant enzyme have been deposited in the Protein Data Bank as entries 2Z72 and 2ZBM respectively Received 15 May 2008 revised 17 June 2008 accepted 26 June 2008 doi 10.1111 j.1742-4658.2008.06575.x The cold-active protein tyrosine phosphatase found in psychrophilic Shewa-nella species exhibits high catalytic efficiency at low temperatures as well as low thermostability both of which are characteristics shared by many coldactive 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 A 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 .
