Ubiquitous endoprotease within constitutive secretory pathways capable of cleavage at the RX(K/R)R consensus motif (    ). Mediates processing of TGFB1, an essential step in TGF-beta-1 activation . Converts through proteolytic cleavage the non-functional Brain natriuretic factor prohormone into its active hormone BNP(1-32) (, ). By mediating processing of accessory subunit ATP6AP1/Ac45 of the V-ATPase, regulates the acidification of dense-core secretory granules in islets of Langerhans cells (By similarity).
(Microbial infection) Cleaves and activates diphtheria toxin DT.
(Microbial infection) Cleaves and activates anthrax toxin protective antigen (PA).
(Microbial infection) Cleaves and activates HIV-1 virus Envelope glycoprotein gp160.
(Microbial infection) Required for H7N1 and H5N1 influenza virus infection probably by cleaving hemagglutinin.
(Microbial infection) Able to cleave S.pneumoniae serine-rich repeat protein PsrP.
(Microbial infection) Facilitates human coronaviruses EMC and SARS-CoV-2 infections by proteolytically cleaving the spike protein at the monobasic S1/S2 cleavage site. This cleavage is essential for spike protein-mediated cell-cell fusion and entry into human lung cells.
(Microbial infection) Facilitates mumps virus infection by proteolytically cleaving the viral fusion protein F.
Subcellular locations: Golgi apparatus, Trans-Golgi network membrane, Cell membrane, Secreted, Endosome membrane
Shuttles between the trans-Golgi network and the cell surface (, ). Propeptide cleavage is a prerequisite for exit of furin molecules out of the endoplasmic reticulum (ER). A second cleavage within the propeptide occurs in the trans Golgi network (TGN), followed by the release of the propeptide and the activation of furin .
Seems to be expressed ubiquitously.