Spectroscopic Studies on the Complexation of Papain with Potassium Poly(Vinyl Alcohol Sulfate)

The complexation of papains (EC.3.4.22.2) with potassium polyvinyl alcohol sulfate) (KPVS) in aqueous solutions as a function of pH was studied using fluorescence spectroscopy. A maximum emission at 333 nm was observed in aqueous diluted papain solutions (concentration < 10−6 mol/dm3) not containing KPVS. As the concentration of papain increased, the positions of the maximum emission were blue shifted; that is, the difference in wavelength from 333 nm increased with an increase in the protein concentration. A similar shift was observed when KPVS was added to papain solutions at a constant concentration (10−6 mol/ dm3) with pH values which had been adjusted to 2 and 7. However, such a shift was not observed at pH 10. In addition, the effect of KPVS on the maximum emission shift was larger at pH 7 than at pH 2. These results are discussed in connection with the protein/protein interaction within an intrapolymer papain/KPVS complex.