Roger D. Wade

The molecular weight of a-chymotrypsinogen

The molecular weight of crystalline a-chymotrypsinogen has been determined from amino acid analysis, light-scattering, and sedimentation-diffusion measurements. The values obtained by the use of these methods are, respectively, 25,100, 26,000 and 24,200. These values, together with the recently reported X-ray estimate of 25,000, converge toward 25,000 as the most probable molecular weight of a-chymotrypsinogen.

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.

The amino acid sequence of the activation peptide of bovine pro-carboxypeptidase A

The amino acid sequence of the activation peptide of bovine pro-carboxypeptidase A subunit I has been determined by automated Edman degradation of the cyanogen bromide fractions derived from the precursor protein. The activation peptide contains 94 amino acid residues in a unique sequence which precedes directly the amino-terminal alanine residue of carboxypeptidase A alpha. A notable feature of the activation peptide is the presence of acidic amino acid residues immediately preceding the site of activation. The amino acid sequence of the activation peptide of bovine pro-carboxypeptidase A shows extensive similarity to those of the corresponding porcine and rat enzymes.