Chymotrypsin C Is a Co-activator of Human Pancreatic Procarboxypeptidases A1 and A2

Richárd Szmola,Melinda Bence,Andrea Carpentieri,András Szabó,Catherine E Costello,John Samuelson,Miklós Sahin-Tóth

doi:10.1074/jbc.m110.187369

Abstract

Human digestive carboxypeptidases CPA1, CPA2, and CPB1 are secreted by the pancreas as inactive proenzymes containing a 94-96-amino acid-long propeptide. Activation of procarboxypeptidases is initiated by proteolytic cleavage at the C-terminal end of the propeptide by trypsin. Here, we demonstrate that subsequent cleavage of the propeptide by chymotrypsin C (CTRC) induces a nearly 10-fold increase in the activity of trypsin-activated CPA1 and CPA2, whereas CPB1 activity is unaffected. Other human pancreatic proteases such as chymotrypsin B1, chymotrypsin B2, chymotrypsin-like enzyme-1, elastase 2A, elastase 3A, or elastase 3B are inactive or markedly less effective at promoting procarboxypeptidase activation. On the basis of these observations, we propose that CTRC is a physiological co-activator of proCPA1 and proCPA2. Furthermore, the results confirm and extend the notion that CTRC is a key regulator of digestive zymogen activation.

Highlights

We identified human chymotrypsin C (CTRC) as a specific regulator of activation and degradation of human cationic trypsinogen and trypsin [8, 9]
Expression and Purification of Human ProCPA1 and ProCPA2—Human proCPA1 and proCPA2 were expressed in transiently transfected HEK 293T cells and purified from the conditioned medium as described under “Experimental Procedures.”
Activation of Human ProCPA1 and ProCPA2 with Trypsin— Procarboxypeptidases (2 ␮M concentration) were incubated with human cationic trypsin (100 nM concentration), and the digestion products were visualized by SDS-PAGE

Summary

Introduction

We identified human CTRC as a specific regulator of activation and degradation of human cationic trypsinogen and trypsin [8, 9]. Chymotrypsin C (CTRC)3 is a digestive protease synthesized and secreted by pancreatic acinar cells as an inactive precursor (chymotrypsinogen C), which becomes activated in the duodenum after trypsin cleaves the Arg29–Val30 peptide bond at the C-terminal end of the propeptide.

Results

Conclusion