Furin is likely to represent the ubiquitous endoprotease activity within constitutive secretory pathways and capable of cleavage at the RX(K/R)R consensus motif. Release of mature proteins from their proproteins by cleavage of -Arg-Xaa-Yaa-Arg-|-Zaa- bonds, where Xaa can be any amino acid and Yaa is Arg or Lys. Releases albumin, complement component C3 and von Willebrand factor from their respective precursors. In adults, isoform 1-X is expressed in CNS, fat body and female reproductive tissues, and in embryos, in CNS, tracheal pits, hindgut, posterior spiracles and anal pads. Isoforms 1-X and 2 are expressed in embryos, larvae, pupae and adults. Highest expression is in late embryos. Belongs to the peptidase S8 family. Furin subfamily.