THERMOINACTIVATION OF CELLOBIOHYDROLASE-I FROM TRICHODERMA-REESEI QM-9414

Irreversible thermoinactivation of cellobiohydrolase I from Trichoderm a reesei has been analyzed at 70 degrees 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 precip itation was the main process leading to irreversible thermoinactivatio n. The enzyme activity was very resistant to 4 M urea which stabilized the enzyme against thermal inactivation. Deamidation of Asn/Gln resid ues and hydrolysis of peptide bonds were responsible for the loss of e nzyme activity at long times of exposure at 70 degrees C.