EC Number   |
General Information |
Reference |
|---|
   3.4.21.43 | malfunction |
inhibition of C3 convertase activity by hepatitis C virus as an additional lesion in the regulation of complement components. Inhibition of C3 convertase activity and C3b deposition onto bacterial membrane by hepatitis C virus, impairment of both C3 convertase and Factor I activity, overview |
732760 |
| 3.4.21.43 | metabolism |
all pathways converge at the level of the C3 molecule, where downstream events can be amplified by a mechanism of positive feedback supported by complement convertases: the classical/lectin pathway C3 convertase (C4b2a) or the alternative pathway C3 convertase (C3bBb). These convertases further cleave C3 to C3b and C3a, of which C3b binds to nearby surfaces, providing a convertase assembly platform, or to pre-assembled C3 convertases, switching them to C5 convertases (C4b2aC3b or C3bBbC3b, respectively). The C5 convertase cleaves C5 molecules to C5a and C5b and the latter initiates formation of the membrane attack complex (MAC, C5b678polyC9) and its insertion into a target membrane. Enzyme regulation, overview |
732705 |
| 3.4.21.43 | metabolism |
further processing of enzyme reaction product C3b results in the formation of iC3b and C3f, and finally C3c and C3dg |
732760 |
| 3.4.21.43 | more |
the classical C5 convertase requires factor D, factor B, and properdin for activation and complex assembly |
732705 |
| 3.4.21.43 | physiological function |
modulation of the upstream proteins involved in proteolytic processing of the complement cascade prior to convertase formation is critical in promoting the function of the complement system in response to infection |
732760 |
| 3.4.21.43 | physiological function |
neither the classical nor the alternative complement pathways are required for disease development of experimental cerebral malaria. C3-/- mice develop severe experimental cerebral malaria through activation of C5 independent of complement C5 convertases by terminal pathway activation. C5 is activated in experimental cerebral malaria through the extrinsic protease pathway, overview. C5-/- mice are highly resistant to experimental cerebral malaria |
732062 |
| 3.4.21.43 | physiological function |
soluble recognition molecule PTX3, i.e. long pentraxin 3, displays multiple functions including innate immune defense against certain microbes and the clearance of apoptotic cells. In addition to complement activators, PTX3 interacts with complement inhibitors including C4BP. This balanced interaction on extracellular matrix and on apoptotic cells may prevent excessive local complement activation that would otherwise lead to inflammation and host tissue damage. PTX3 binds to the classical and lectin pathway regulator C4b-binding protein C4BP. A PTX3-binding site lies within short consensus repeats 1-3 of the C4BP a-chain. PTX3 does not interfere with the cofactor activity of C4BP in the fluid phase and C4BP maintains its complement regulatory activity when bound to PTX3 on surfaces. PTX3 binds to human fibroblast- and endothelial cell-derived extracellular matrices and recruits functionally active C4BP to these surfaces. Whereas PTX3 enhances the activation of the classical/lectin pathway and causes enhanced C3 deposition on extracellular matrix, deposition of terminal pathway components and the generation of the inflammatory mediator C5a are not increased. PTX3 enhances the binding of C4BP to late apoptotic cells, which resultes in an increased rate of inactivation of cell surface bound C4b and a reduction in the deposition of C5b-9 |
718289 |
| 3.4.21.43 | physiological function |
zymosan activates the classical pathway by an antigen-antibody reaction in normal human serum requiring IgG and IgM antibodies, it cannot initiate classical pathway activation without the antibodies, regulation, overview |
732572 |
