Thermoinactivation of cellobiohydrolase I from Trichoderma reesei QM 9414

Irreversible thermoinactivation of cellobiohydrolase I from Trichoderma reesei has been analyzed at 70°C and pH 4.8. The time course of thermal inactivation and the dependence of the inactivation rates on protein concentration suggested that aggregation followed by precipitation was the main process leading to irreversible thermoinactivation. The enzyme activity was very resistant to 4 M urea which stabilized the enzyme against thermal inactivation. Deamidation of Asn/Gln residues and hydrolysis of peptide bonds were responsible for the loss of enzyme activity at long times of exposure at 70°C.