We have recently demonstrated, by protein and cDNA sequence analysis, that prorenin converting enzyme (PRECE) in the mouse submandibular gland is identical to the epidermal growth factor-binding protein (EGF-BP)type B. However, type A and C did not show prorenin converting activity. To demonstrate whether r-NGF is involved in prorenin processing, we have cloned cDNA of r-NGF and examined prorenin converting activity using the CHO cell expression system, Trypsin converted the 33 kDa r-NGF precursor produced in CHO cells to a two-chain form, 9.4 and 16.4 kDa polypeptide chains, which has been known as an active form of r-NGF in mouse SMG (Server and Shooter, 1976). However, the two chain forms of r-NGF did not reveal prorenin-processing activity. Thus, only PRECE is involved in prorenin processing in mouse SMG. This result shows that their substrate specificities appear to be very strict, although some kallikreins share a high degree of amino acid sequence identity.