Chymotrypsinogen D, a new zymogen from porcine pancreas with proelastolytic activity.

During the purification of propancreatopeptidase E, a proATEEase activity is always copurified. The proelastolytic and proesterolytic activities can be separated on a hydroxylapatite column. The zymogen with potential ATEEase activity has a basic isoelectric point, can be activated by trypsin, and can hydrolyse elastin and ATEE but not ATAME. Its molecular weight is about 26,500 and the NH2-terminal sequence indicates clearly that it belongs to the chymotrypsinogen family, but that it is not chymotrypsinogen A, B, or C. We call it chymotrypsinogen D. Although both pancreatopeptidase E and chymotrypsin D can hydrolyse elastin, the synthetic substrate ATAME is attacked only by pancreatopeptidase E. Therefore, the peptide bonds in elastin cleaved by these two enzymes should be different.