“Thermal inactivation analysis of extracellular proteases obtained from a sub-antarctic Colwellia isolate”

NIEVAS, M.L., SEQUEIROS, C., AND OLIVERA, N.L.

Pinamar, Argentina

Congreso; XLI Reunión Anual SAIB y X Congreso Panamericano PABMB; 2005

SAIB

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 a 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 applying the transition state theory. Over the studied temperature range Eain, ∆Hin* and ∆Sin* were almost constant with values of 181.5 kJ mol-1, 178.9 kJmol-1 and 0.27 kJ mol-1K-1, while ∆Gin* was between 99.3-91.2 kJ mol-1. Colwellia sp. IE1-3 proteases showed higher thermosensitivity than most of bacterial enzymes, being the ∆Gin* value obtained comparable to those of the few psychrophilic proteases characterized to date.