Rhodanese persulfide group

A third spectral perturbation is induced at 290 nm by cyanide treatment of rhodanese which is still present upon addition of thiosulfate (see Fig.2). This finding indicates that the cleavage of rhodanese persulfide group by cyanide causes a perturbation of (a) trypto-phanyl residue(s) which is not reversed by a sulfur donor substrate. Since x-ray studies show that trypto-... 

These results allow to correlate these absorbance changes with the presence of persulfide group in the enzyme molecule. The differential molar extinction coefficients for sulfur-free and sulfur-containing rhodanese were found to hezAs2j( = 550, As22 120 these values are very close to those obtained for persulfurated serum albumin and glutathione (see Table l). 

Table I - Differential molar extinction coefficients of persulfide group in artificially persulfurated compounds and in sulfur-rhodanese.

The restoration of the persulfide group in the rhodanese molecule by addition of thiosulfate lead to similar changes in absorption and CD spectra (Fig. 2,4 and 5). The optically active band at 308 nm present in the native molecule is still present together with a new positive band at 330 nm. These bands occur at similar wavelength where the persulfurated glutathione is optically active. The above mentioned irreversible perturbation of tryptophanyl residue(s), as a consequence of a modification of the active site, can explain also the different absorban-... 

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