ENTRY       EC 3.4.21.43
NAME        Classical-complement pathway C3/C5 convertase
            Complement C2
            C3 convertase
            C5 convertase
CLASS       Hydrolases
            Acting on peptide bonds (peptidases)
            Serine endopeptidases
REACTION    Selective cleavage of Arg+Ser bond in complement component C3
            alpha-chain to form C3a and C3b, and Arg+ bond in complement
            component C5 alpha-chain to form C5a and C5b
SUBSTRATE   H2O
            Peptide
PRODUCT     Peptide
COMMENT     A complex of complement fragments C4b, C2a and C2b.  C2a contains
            the active site, C2b the site for C4b binding.  C2a and C2b are
            formed by cleavage of proenzyme C2 by complement subcomponent C1s.
            Cleavage of C5 requires complement fragment C3b which binds C5 and
            renders it susceptible to cleavage by the C4b, 2a complex.
            INcludes former EC 3.4.21.44.
DISEASE     MIM: 217000  Complement component-2; C2 deficiency (3)
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: C3
DBLINKS     University of Geneva ENZYME DATA BANK: 3.4.21.43
            WIT (What Is There) Metabolic Reconstruction: 3.4.21.43
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