N-ARGININE DIBASIC CONVERTASE (NRD CONVERTASE) - A NEWCOMER TO THE FAMILY OF PROCESSING ENDOPEPTIDASES - AN OVERVIEW

N-arginine dibasic convertase (NRD convertase) (accession number L2712 4) is a metalloendopeptidase from rat brain cortex and testis which cl eaves peptide substrates on the N-terminus of arginine residues in bas ic doublets. Its predicted amino acid sequence contains the putative z inc binding motif HXXEH in a region which exhibits 35% and 48% similar ity with E coli protease m (pitrilysin E.C 3.4.99.44) and rat or human insulinase (E.C 3.4.99.45) respectively. This feature clearly classif ies this endopeptidase;as a member of the pitrilysin family of zinc-me talloproteases. However, the NRD convertase sequence contains a distin ctive additional feature consisting of a 71 acidic amino acid stretch. Its substrate selectivity and the characteristic motifs of its amino acid sequence allow us to propose this new metalloendopeptidase as the first member of a new class of processing enzymes.