Comparison of the ribonucleolytic activity of the dityrosine cross-linked Ribonuclease A dimer with its monomer in the presence of inhibitors

Dityrosine cross-linking is considered to be one of the major reasons behind natural protein dimerization. Reports have shown that dimers of Ribonuclease A prepared by several methods exhibit reduced ribonucleolytic activity compared to the native monomer. Here in the present report, a detail investigation has been carried out to determine the effect of dityrosine cross-linking of Ribonuclease A on its ribonucleolytic activity. We have also studied the inhibitory property of natural, competitive and noncompetitive inhibitors on the catalytic activity of the dimer. The dimer was prepared by photo irradiation of Ribonuclease A using riboflavin as a photo sensitizer followed by separation using size exclusion chromatography. The dimer has been characterized via gel electrophoresis and various spectroscopic techniques. Experimental findings suggest that the synthesized dityrosine cross-linked dimer of Ribonuclease A exhibits reduced ribonucleolytic activity in comparison with the monomeric form both in the presence and absence of the inhibitors