C3-convertase: Difference between revisions
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There are two forms of '''C3-convertase''' ({{EC number|3.4.21.43}}). |
There are two forms of '''C3-convertase''' ({{EC number|3.4.21.43}}). |
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The first is an [[enzyme]] composed of the C4b- |
The first is an [[enzyme]] composed of the C4b-C2b complex, which forms during the [[Classical complement pathway|Classical pathway]] of the [[complement system]]. It is formed when [[C1s]] cleaves off [[C2a]] from a membrane-bound C4b-C2 complex. |
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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. |
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. |
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Revision as of 02:54, 28 January 2007
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.
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