3.4.21.43: classical-complement-pathway C3/C5 convertase
This is an abbreviated version!
For detailed information about classical-complement-pathway C3/C5 convertase, go to the full flat file.
Word Map on EC 3.4.21.43
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 =
Synonyms
C3 convertase, C3/C5 convertase, C3b 2 Bb, C3b2Bb, C3bBb, C3bBbP, C4, C423, C4b,2a, C4b,2a,3b, C4b,C2a, C4b2a, C4b2a(C3b)n, C4b2a3b, C4b2aC3b, C4bC2a, C5 convertase, classical C3 convertase, classical C5 convertase, classical pathway C3 convertase, classical pathway C3/C5 convertase, classical pathway C5 convertase, complement C3 convertase, CP C3 convertase, CP C3/C5 convertase, CP C5 convertase, EAC1,C4b,C2a, EC 3.4.21.44, high affinity C5 convertase, soluble C3 convertase, surface-bound C3 convertase
ECTree
3.4.21.43 classical-complement-pathway C3/C5 convertaseAdvanced search results
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Activating Compound on EC 3.4.21.43 - classical-complement-pathway C3/C5 convertase
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ACTIVATING COMPOUND 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
IMAGE
C3b
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both the soluble form of the enzyme, C4b,C2a and the surface-bound form of the enzyme EAC1,C4b,C2a exhibit a poor affinity for the substrate C5. Very high affinity C5 convertase is generated only when the low affinity C3/C5 convertases are allowed to deposit C3b by cleaving native C3
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complement component C3b
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in inactive surface-fixed form essential for cleavage of C5
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factor B
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the classical C5 convertase requires factor D, factor B, and properdin for activation and complex assembly
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factor D
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the classical C5 convertase requires factor D, factor B, and properdin for activation and complex assembly
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properdin
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the classical C5 convertase requires factor D, factor B, and properdin for activation and complex assembly
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zymosan
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it is capable of activating the classical pathway as well as the alternative pathway, when the classical pathway is blocked, mechanism, overview
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additional information
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cooperation of the enzyme with MBL-associated serine proteases MASP-1 and MASP-2 in C3 cleavage, the serine proteases generate active C3 convertase at high serum concentration, while MASP-3 inhibits it, overview
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additional information
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properdin can initiate complement activation by binding specific target surfaces, e.g. microbial targets like Neisseria gonorrhoeae, and Escherichia coli and Salmonella typhimurium lipopolysaccharide mutants, or yeast cell walls, , and providing a platform for de novo convertase assembly and function via the alternative pathway, overview, recombinant human compound
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additional information
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complement activation via the lectin pathway on zymosan particles is at least 4times more efficient than via the classical pathway on sheep erythrocytes coated with antibody. Every C4b deposited via the lectin pathway is capable of forming a convertase in contrast to only one of four C4b molecules deposited via the classical pathway. Rate of formation of lectin pathway C3/C5 convertases depends on the activation of C4 and C2 by MASP-2
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additional information
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molecular interactions between MASP-2, C4, and C2 and their activation fragments leading to complement activation via the lectin pathway, overview
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