Catalytic Efficiency and Some Structural Properties of Cold-Active Protein-Tyrosine-Phosphatase

Abstract

A procedure was established for expression and purification of abundant recombinant cold-active protein-tyrosine-phosphatase (RCPTPase), which showed identical enzymatic characteristics to the native enzyme (NCPTPase). The purified RCPT-Pase showed high catalytic activity at low temperature and maximal activity at 30°C. RCPTPase has a thermodynamic characteristic in that its activation enthalpy was determined to be low, 4.3 kcal/mol, at temperatures below 19.3°C, where the Arrhenius relationship exhibited an inflection point, in comparison with 20.3 kcal/mol above 19.3°C. Also, the thermostability, ΔG_water, of the catalytic site in the RCPTPase molecule was increased with a decrease in temperature. It was considered that cold-active protein-tyrosine-phosphatase could maintain its catalytic site in a stable conformation for eliciting high catalytic activity with low activation enthalpy at low temperature.