Effect of urea on the structure and functional activity of proteins. Chymotrypsinogen A and α-chymotrypsin

Abstract

The effect of urea on the structural stability and functional activity of globular proteins,viz., chymotrypsinogen A (ChtG) and α-chymotrypsin (Cht), was studied over a wide range of concentrations (0.5–6 rnol L-1), and the existence of two different mechanisms of the action of urea on these proteins was demonstrated. No changes in the spatial structure of ChtG were observed in the concentration range from 0,5 to 3 mol L−1 (region 1). Differential UV spectroscopy shows tile redistribution of aromatic groups between the inner volume and the outer surface of a protein molecule (protein denaturation) at concentrations >3 mol L−1 (regionII), In regionI, urea changes the kinetic parameters of enzymatic reactions involving Cht, which is explained on the basis of millimeter spectroscopy data by its action on the structure and nucleophilic reactivity of water.