C3-convertase
Encyclopedia : C : C3 : C3C : C3-convertase
There are two forms of C3-convertase (EC [3.4.21.43]).
The first is an enzyme composed of the C4b-C2b complex, which forms during the Classical pathway of the complement system. It is formed when C1s cleaves off C2a from a membrane-bound C4b-C2 complex.
The second consists of the C3bBb complex, which forms during the alternative complement pathway. It is formed when membrane bound C3b binds to factor B which is in turn cleaved by factor D in Ba and Bb. Bb remains bound to C3b while Ba is released into the surrounding medium.
Once formed, both C3-convertases will catalyze the proteolytic cleavage of C3 into C3a and C3b (hence the name "C3-convertase"). C3b can then act as an opsonizer or itself become a C3-convertase.
| Complement system - [http://encycl.opentopia.com/ edit] |
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Activators:
C6 |
C7 |
C9 |
MBL2 |
PFC
Complexes: C1Q (C1QA, C1QB, C1QG) | C3-convertase | C8 (C8A, C8B, C8G) | MAC Enzymes: BF | C1R | C1S | C2 | C3 | C4 | C5 | DF | MASP1 | MASP2 Inhibitors: C1inh | C4BP (C4BPA, C4BPB) | CLU | DAF | HF1 | IF | SERPING1 | VTN Receptors: C3AR1 | C5R1 | CR1 | CR2 | ITGAM |
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