The heat-inactivation of the proteinase of the pancreas.

INTRODUCTION. WHILE previous work of the writer, upon the heat inactivation of trypsin, was in progress, it was shown by Waldschmidt-Leitz and Purr [1929] that trypsin itself is not an individual enzyme, but that it may be resolved into two components-a proteinase and a carboxypolypeptidase. It was found by these authors that the proteinase, although completely inactive alone, is capable, when associated with enterokinase, of hydrolysing proteins and certain of their degradation products. The carboxypolypeptidase, in the absence of enterokinase, attacks a number of polypeptides and some dipeptides, which possess a free carboxyl group in the molecule, but will not attack a protein. Enterokinase increases the activity of carboxypolypeptidase. This work of Waldschmidt-Leitz and Purr has a distinct bearing upon the interrelation of trypsin and enterokinase. It is of interest to recall, very briefly, the views which have been held about this problem. (a) The "classical" view. It was considered that an inactive zymogen, trypsinogen is produced in the pancreas. The trypsinogen is enzymically transformed into trypsin by enterokinase, and the trypsin thus produced is able to hydrolyse proteins. This may be expressed thus: