Caldecrin proform requires trypsin activation for the acquisition of serum calcium-decreasing activity.

Proform serum calcium-decreasing factor (procaldecrin) was purified from porcine pancreas acetone powder. Procaldecrin showed chymotrypsin activity after trypsin treatment in a time- and dose-dependent manner. Procaldecrin did not possess serum calcium-decreasing activity but acquired serum calcium-decreasing activity as well as protease activity after trypsin treatment. However, PMSF treatment after activation of procaldecrin by trypsin did not affect the serum calcium-decreasing activity, even though protease activity was nullified by treatment with PMSF. These findings suggest that the serum calcium-decreasing activity acquired by procaldecrin requires conformational change caused by trypsin treatment.