William J. Dreyer

Structural changes in the activation of chymotrypsinogen and trypsinogen. Effect of urea on chymotrypsinogen and delta-chymotrypsin

Abstract In an attempt to detect structural differences between chymotrypsinogen and chymotrypsin, and trypsinogen and trypsin, measurements of the optical rotation and of the enzymatic activity of these proteins were carried out. The results indicate that the decrease in specific levorotation on activation of these zymogens is correlated with the appearance of enzymatic activity, and that the structure of the active enzyme is more sensitive to pH changes than that of the zymogen. Measurements of the effect of urea on optical rotation, viscosity, and biological activity of chymotrypsinogen and δ-chymotrypsin are also reported in this communication. These include the effects of time and urea concentration on the measured parameters. On the basis of the data presented, in conjunction with other information on the chemical and physical characteristics of chymotrypsinogen and δ-chymotrypsin, tentative conclusions have been drawn concerning the structural changes involved in activation and denaturation, respectively.

Observations on the electrophoretic and ultracentrifugal changes accompanying the activation of chymotrypsinogen.

Abstract Electrophoretic and ultracentrifugal measurements of chymotrypsinogen, of rapid and slow activation mixtures, and of crystalline chymotrypsins are described. Whereas chymotrypsinogen and rapid activation mixtures show a relatively high degree of electrophoretic homogeneity, the electrophoretic patterns become more complex and heterogeneous as the time of activation increases and the rate decreases. The DIP derivatives of crystalline, α-, β-, and γ-chymotrypsins are among the most heterogeneous products of this series of proteins. All of these proteins exist as a monomer at pH 3, within the concentration range of 2–20 mg./ml. In contrast to chymotrypsinogen, which is monomeric over the entire pH range studied, DIP-π- and -δ-chymotrypsins at pH 7.5 exist in concentration-dependent monomer-dimer equilibrium. The pH dependence of dimerization of the crystalline enzymes differs markedly from those of the above proteins.