Figure 4. a. Sequence analysis of different pancreatic and duodenal proteins revealed a putative BACE1 cleavage site (red) within the catalytic active light chain of enteropeptidase. Given the molecular weight of 35 kDa of bovine enteropeptidase light chain, cleavage of enteropeptidase at this position would theoretically result in two fragments of 25 kDa and 10 kDa. b. Bovine enteropeptidase was incubated with recombinant BACE1. At the indicated times, samples were withdrawn and separated by SDS-polyacrylamide gel electrophoresis. Protein staining revealed the presence of BACE1 (green arrow), enteropeptidase (red arrow), and additional bands of the estimated molecular weight of enteropeptidase cleavage products (red arrowheads).