Also called enteropeptidase. Be careful as Enteropeptidase can be a bit misleading since the ending is -ase, and like the other enzymes present here, you don't want to mess up and think it breaks peptides down! Instead it breaks down trypsinogen, inactive, into trypsin, active, which goes on to cleave other inactive enzymes like carboxypeptidase, chymotripsinogen, etc. into their respective active forms.