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Author (up) Bourne, G.L.; Grainger, D.J. file  url
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  Title Development and characterisation of an assay for furin activity Type Journal Article
  Year 2011 Publication Journal of Immunological Methods Abbreviated Journal J Immunol Methods  
  Volume 364 Issue 1-2 Pages 101-108  
  Keywords Anoxia/diagnosis/genetics/*metabolism; Antibodies/immunology/*metabolism; Biochemistry/methods; Cell Extracts/chemistry; Furin/*genetics/immunology/*metabolism; Gene Expression Regulation, Enzymologic; Hep G2 Cells; Humans; Immunomodulation; *Immunosorbent Techniques; RNA, Messenger/*analysis; Reference Standards; Sensitivity and Specificity; Transforming Growth Factor beta/immunology/metabolism  
  Abstract Furin is a serine endoprotease that is responsible for the proteolytic processing of proteins within the secretory pathway, including cytokines, hormones, integrins, other proteases, and also pathogen-derived proteins. It is likely that the level of furin activity determines the extent of processing of these substrates. Furin is ubiquitously expressed across all tissues, at low levels, but can be induced in response to environmental cues such as hypoxia and cytokine stimulation. However, all studies to date that have investigated furin expression have been limited to analysis of furin mRNA; there has been no assay sensitive enough to quantify endogenous furin. Though activity-based assays have been described for furin-like enzyme activity, we demonstrate that these assays are dominated by the activity of other enzymes and cannot be used to approximate furin activity. A sensitive and specific assay for furin activity was therefore developed and characterised, using an antibody capture step to immobilise furin from whole cell lysates. Furin activity is quantified relative to that of recombinant active furin protein, to allow estimation of active furin protein concentration. The assay has a minimum detection limit of 0.006 nM; sensitive enough to determine the furin activity of many of the cell lines tested. The specificity of the assay was demonstrated by genetic modulation of furin expression. Furthermore, the assay was used to demonstrate that the cytokine transforming growth factor beta (TGF-beta) stimulates increased furin activity in HepG2 cells, confirming and extending previous reports that TGF-beta increases furin expression, and adding to the mounting body of evidence that cellular furin activity can be modulated.  
  Call Number Serial 525  
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Author (up) Van de Ven, W.J.; Creemers, J.W.; Roebroek, A.J. file  url
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  Title Furin: the prototype mammalian subtilisin-like proprotein-processing enzyme. Endoproteolytic cleavage at paired basic residues of proproteins of the eukaryotic secretory pathway Type Journal Article
  Year 1991 Publication Enzyme Abbreviated Journal Enzyme  
  Volume 45 Issue 5-6 Pages 257-270  
  Keywords Animals; Binding Sites; Catalysis; Cloning, Molecular; Drosophila melanogaster; Furin; Humans; Invertebrate Hormones/genetics/metabolism; Mice; Models, Molecular; Multigene Family; Protein Conformation; Protein Precursors/*metabolism; *Protein Processing, Post-Translational; Sequence Homology, Amino Acid; Substrate Specificity; Subtilisins/genetics/*metabolism  
  Abstract Furin, the translational product of the recently discovered fur gene, appears to be the first known mammalian member of the subtilisin family of serine proteases and the first known mammalian proprotein-processing enzyme with cleavage selectivity for paired basic amino acid residues. Structurally and functionally, it resembles the prohormone-processing enzyme, kexin (EC 3.4.21.61), which is encoded by the KEX2 gene of yeast Saccharomyces cerevisiae. Most likely, furin is primarily involved in the processing of precursors of proteins that are secreted via the constitutive secretory pathway. Here, we review the discovery of the fur gene and describe the isolation of cDNA clones corresponding to human and mouse fur and to two fur-like genes of Drosophila melanogaster, Dfur1 and Dfur2. We also compare the structural organization of the various deduced furin proteins to that of yeast kexin, and of other members of the subtilisin family of serine proteases. Furthermore, the biosynthesis of biologically active human and mouse furin is evaluated. Finally, the cleavage specificity for paired basic amino acid residues of human and mouse furin is demonstrated by the correct processing of the precursor for von Willebrand factor.  
  Call Number Serial 524  
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