The self-association of chymotrypsinogen

The self-association of chymotrypsinogen A is reduced by decreasing the pH below pH 8 or by an increase in electrolyte level. The latter effect is correlated with ionic strength for several electrolytes with different properties. The self-association in H₂O is almost independent of temperature. Substitution of D₂O for H₂O increases the extent of association. Conversion of the two reactive tyrosines to nitrotyrosine extends the zone of stability of the complex species to more acid pH. From these results it is concluded that the dominant stabilizing force is electrostatic in origin, but that hydrophobic forces also make a significant contribution.