Increased thermal and organic solvent tolerance of modified horseradish peroxidase. Protein Eng. Des. Selection 19, 169173 Activity and stability of a protease in organic solvents at Pennsylvania State U niversity on Septem ber 12, 2016 http://jb.oxfordjo

Horseradish peroxidase (HRP) was modified by maleic anhydride and citraconic anhydride. The thermal and organic solvent tolerances of native and modified enzyme were compared. These chemical modifications of HRP increased their thermostability both in aqueous buffer and some organic solvents, and also enhanced their toler-ances of some organic solvents. We have studied the unfold-ing of native and modified HRP by heat to determine the conformational stability. The temperature at the midpoint of thermal denaturation (Tm) was increased upon modifica-tion. Both enthalpy change (DHm) and entropy change (DSm) for unfolding of modified enzyme at Tm were decreased compared with native enzyme. Circular dichro-ism studies proved that these modifications changed the con-formation of HRP. The improvements of stability are related to side chain reorientations of aromatics upon both modifications