Penicillopepsin from Penicillium janthinellum crystal structure at 2.8 A and sequence homology with porcine pepsin.

The polypeptide chain of the acid protease penicillo pepsin folds via an 18-stranded mixed beta-sheet into two distinct lobes separated by a 30-A long groove which is the extended substrate binding site. The catalytic residues Asp-32 and Asp-215 are located in this groove and their carboxyl groups are in intimate contact. Alignment of the amino acid sequence with that of pepsin shows regions of high homology.