Thought to be involved in the hydrolysis of stored seed proteins. In vitro, catalyzes the hydrolysis of proteins, such as azocasein. Shows a preferential cleavage for Asn-|-Xaa in small molecule substrates such as Boc-Asn-|-OPHNO(2). The mature protein is not glycosylated. The precursor stored in the endoplasmic reticulum lumen is processed during the transport to proteins bodies to two dominant mature forms that differ by a single amino acid residue at the N-terminus. Belongs to the peptidase C1 family.