Unfolding of Plasmodium falciparum triosephosphate isomerase in urea and guanidinium chloride: evidence for a novel disulfide exchange reaction in a covalently cross-linked mutant

The conformational stability of Plasmodium falciparum triosephosphate isomerase (TIMWT) enzyme was studied in urea and guanidinium chloride (GdmCl) solutions by circular dichroism, fluorescence and size-exclusion chromatography. The dimeric enzyme was observed to be stable in urea solutions. It retained a substantial secondary, tertiary and quaternary structure even in 8 M urea. On the other hand, the unfolding transition was completed by 2.5 M GdmCl.