Nardilysin (NRD1)

Endoproteases that activate protein precursors by cleavage at basic residues belong to the 4 classes of proteases: aspartyl, serine, thiol, and metalloenzymes. NRD1, a metalloendopeptidase that cleaves peptide substrates at the N terminus of arginine residues in dibasic moieties, had been previously purified from rat testis. By screening a rat testis cDNA library with oligonucleotides based on the sequence of the purified Nrd1 protein, The predicted 1,161-amino acid Nrd1 protein has a calculated molecular mass of 133 kD, consistent with the mass of the largest form of the purified enzyme. Nrd1 contains a putative signal peptide, a 71-residue acidic stretch, and a zinc-binding motif. The amino acid sequence of rat Nrd1 is 31% identical to that of human insulinase (IDE).