DENATURATION OF HORSERADISH-PEROXIDASE WITH UREA AND GUANIDINE-HYDROCHLORIDE

Favourable effects of urea and guanidine hydrochloride (Gdn HCl) on so lubilization of the polar, non-polar and peptide groups of horseradish peroxidase (HRP), an example of a globular protein, provide the drivi ng force for unfolding of HRP, in a reversible two-state process. The intrinsic or conformational stability of HRP at various pH values and temperatures has been estimated by the linear extrapolation method (LE M), a denaturant binding model (DBM) and Tanford's model. There is goo d agreement between these methods. Tanford's model shows that urea int eracts with non-polar groups to a greater extent than Gdn HCl does, wh ereas Gdn HCl interacts more effectively with the peptide groups of HR P.