ENTRY       EC 3.4.21.47
NAME        Alternative-complement pathway C3/C5 convertase
            Complement factor B
            Complement component C3/C5 convertase (alternative)
            Properdin factor B
            C3 proactivator
            C3 convertase
            C5 convertase
CLASS       Hydrolases
            Acting on peptide bonds (peptidases)
            Serine endopeptidases
REACTION    Cleavage of Arg+Ser bond in complement component C3 alpha-chain to
            yield C3a and C3b, and Arg+ bond in complement component C5
            alpha-chain to yield C5a and C5b
SUBSTRATE   Peptide
            H2O
PRODUCT     Peptide
COMMENT     A bimolecular complex of complement fragment Bb with either C3b or
            cobra venom factor; Bb contains the active site. Bb is formed by
            cleavage of proenzyme Factor B by Factor D.  Cleavage of
            complement component C5 requires additional C3b which binds C5 and
            renders it susceptible to cleavage by C3b,Bb complex.  C3b,Bb is
            stabilized in plasma by Factor P.
DISEASE     MIM: 138470  Properdin factor B
MOTIF       PS: PS00134  [LIVM]-[ST]-A-[STAG]-H-C
            PS: PS00135  [DNSTAGC]-[GSTAPIMVQH]-x(2)-G-[DE]-S-G-[GS]-[SAPHV]-
                         [LIVMFYWH]-[LIVMFYSTANQH]
GENES       HSA: BF(Hs.69771)
DBLINKS     University of Geneva ENZYME DATA BANK: 3.4.21.47
            WIT (What Is There) Metabolic Reconstruction: 3.4.21.47
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