Involved in programmed cell death. Shows a pronounced preference for hydrophobic residues in the P2 position and no obvious preference in the P1 position of the cleavage site. Accepts proline at the P1 and P1' positions. Low pH triggers activation of the protease and removal of the propeptide and the KDEL motif. The pro-endopeptidase accumulates in the ricinosomes. Released during the final stage of cellular desintegration in the senescing endosperm of germinating bean. The potential N-glycosylation site at Asn-115 is not glycosylated. The pro-endopeptidase goes directly from the ER lumen to the ricinosome, and the secretory pathway via the Golgi apparatus is not involved in the ricinosome biogenesis. Belongs to the peptidase C1 family.