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THERMAL INACTIVATION ANALYSIS OF EXTRACELLULAR PROTEASES OBTAINED FROM A SUB-ANTARCTIC COLWELLIA ISOLATE
MARINA NIEVAS; CYNTHIA SEQUEIROS; NELDA OLIVERA
Pinamar, Buenos Aires.
Congreso; X Congress of the Panamerican Association of Biochemistry and Molecular Biology (PABMB), XLI Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology (SAIB) and XX Annual Meeting of the Argentine Society for Neurochemistry (SAN); 2005
Argentine Society for Biochemistry and Molecular Biology, Argentine Society of Neurochemistry, Panamerican Society for Biochemistry and Molecular Biology
High activity at low temperature along with a limited thermal stability characterize cold-active enzymes, also named psychrophilic enzymes. Thermostability is one of the main features that determine the technological usefulness of such enzymes. In this study, the thermal stability of extracellular proteases produced by the sub-Antarctic bacterium Colwellia sp. IE1-3 was described by thermal kinetic and thermodynamic apparent parameters. Protease activity was measured using casein as substrate; the remaining activities at 25°C, after incubation of the enzyme extract without substrate in the temperature range 20-50ºC, were determined. The kinetic of thermal inactivation was predicted with an irreversible first order deactivation model. kin values were calculated from the ln (v/v0) vs. time, activation energy (Ea) from Arrhenius plot, and thermodynamic activation parameters from the transition state theory. Over the studied temperature range Eain, deltaHin* and deltaSin* were almost constant with values of 181.5 kJ mol-1, 178.9 kJ mol-1 and 0.27 kJ mol-1K-1, while deltaGin* was between 99.3-91.2 kJ mol-1. Colwellia sp. IE1-3 proteases showed higher thermosensitivity than most of the bacterial enzymes, and the deltaGin* value obtained was comparable to those of the few psychrophilic proteases characterized to date.