Sorting receptor that directs prohormones to the regulated secretory pathway. Acts also as a prohormone processing enzyme in neuro/endocrine cells, removing dibasic residues from the C-terminal end of peptide hormone precursors after initial endoprotease cleavage. Release of C-terminal arginine or lysine residues from polypeptides. Binds 1 zinc ion per subunit. Interacts with secretogranin III/SCG3. Associated with the secretory granule membrane through direct binding to lipid rafts in intragranular conditions. Defects in Cpe are the cause of the fat phenotype. Mice homozygous for the fat mutation develop obesity and hyperglycemia that can be suppressed by treatment with exogenous insulin. Belongs to the peptidase M14 family.