The Complex Nature of Proelastase, a Propeptidase, and Associated Protein

A proenzyme (hereafter propeptidase), with a high activity on N -acetyl- l -tyrosine ethyl ester, was found associated with proelastase through several steps of purification. Propeptidase is distinct from chymotrypsinogen A as shown by its electrophoretic mobility and its high resistance, in the activated form, to inhibition by l -1-tosylamido-2-phenyl-ethyl chloromethyl ketone. Evidence indicates that propeptidase is probably the proenzyme form of elastomucase. Activation of proelastase and propeptidase with trypsin changed their electrophoretic mobilities. The activated proelastase migrated at the same rate as authentic, pure elastase. The proenzymes that were originally highly insoluble could be solubilized by treatment with alumina Cγ gel. The solubilizing effect of alumina Cγ gel was reversible. The solubilized proenzymes could be reprecipitated by recombination with the eluate of alumina Cγ gel. Activation of the proenzymes had no effect on their precipitation with Cγ eluate. To a lesser degree, trypsin and chymotrypsinogen A also precipitated upon mixing them with Cγ eluate. Proelastase and propeptidase each were obtained in an electrophoretically pure state by column chromatography on hydroxylapatite.