Dissociation and unfolding of sulfhydryl oxidase in solutions of guanidinium chloride.

Sulfhydryl oxidase was dissociated completely in 5 M guanidinium chloride as indicated by light scattering molecular weight studies giving masses of 80,000 to 90,000 daltons. Concentrations of guanidinium chloride above 2 M resulted in loss of enzymatic activity and caused extensive unfolding of the enzyme as shown by fluorescence measurements. Replacement of the denaturant with physiological buffers restored native fluorescence characteristics, but the enzyme remained partially dissociated, with a molecular weight of 300,000 to 360,000, enzymatic activity was not restored.