Pro-(carboxypeptidases A) from whole pig pancreas. Their mass, size, shape and solvation

Sedimentation analysis and light-scattering measurements were made with the two forms of pig pancreas pro-(carboxypeptidase A), in order to determine some of their physical properties. The following values were found (the first value applies to the binary complex and the second one to the monomer). The A 1%/280.1 cm values were 19.9 +/- 0.3 and 16.3 +/- 0.3. The partial specific volumes v -0 were 0.707 +/- 0.016 cm3/g and 0.714 +/- 0.015 cm3/g. The sedimentation coefficients S 0/20,w were 4.90 +/- 0.15S and 3.75 +/- 0.15 S. The diffusion coefficients D 0/20,w were (5.8 +/- 0.1) X 10(-7) cm2/s and (6.95 +/- 0.15) X 10(-7) cm2/s. From these data the following values were calculated. Relative molecular masses Mr were 71 000 +/- 4000 and 46 000 +/- 3000. The frictional ratios f/fmin. were 1.37 +/- 0.06 and 1.31 +/- 0.07; assuming a value for the solvation of the molecules (delta = 0.5 g/g) the asymmetry values range from 3 to 5 for the binary complex and from 2 to 4 for the monomer. The Mr values found in the present work coincide with those found by means of polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate [Martínez, Avilés, SanSegundo & Cuchillo (1981) Biochem. J. 197, 141-147]. Therefore the low values obtained by those authors when using gel-filtration chromatography must be the result of the interaction of the zymogens with the gel matrix, as the asymmetry is too small to justify the large discrepancies found.