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c3 convertase การใช้

ประโยคมือถือ
  • The resultant complex, C3bBb, is called the alternative pathway ( AP ) C3 convertase.
  • The larger C2a produced by C2 hydrolysis can then attach to the C4b to form the classical C3 convertase.
  • C2a is the larger, enzymatically active fragment which is incorporated into the C3 convertase in this pathway, C4b2.
  • DAF acts on C2a and Bb and dissociates them rapidly from C4b and C3b  thereby preventing the assembly of the C3 convertase.
  • This cleavage can occur via three mechanisms ( alternative pathway and lectin pathway ) that ultimately lead to the formation of a C3 convertase.
  • C3 convertase can be used to refer to the form produced in the alternative pathway ( C3bBb ) or the classical and lectin pathways ( C4bC2a ).
  • All pathways culminate in the production of a C3 convertase, which catalyses C3 into its constitutive parts ( better detailed here-classical complement pathway ).
  • The stabilized C3 convertase, C3bBbP, then acts enzymatically to cleave much more C3, some of which becomes covalently attached to the same surface as C3b.
  • Once the alternative C3 convertase enzyme is formed on a pathogen or cell surface, it may bind covalently another C3b, to form C3bBbC3bP, the C5 convertase.
  • "' C4 binding protein "'( C4-bp ) interferes with the assembly of the membrane-bound C3 convertase of the classical pathway.
  • C4 binding protein and C3b inactivator control the C3 convertase of the classical pathway in a similar way to that described for ?1H and C3b inactivator in the alternative pathway.
  • Formation of a C3 convertase functions as a positive feedback loop, so as more C3b is cleaved, more C3 convertases are formed, further amplifying the signal on the surface the microbial invader.
  • The smaller fragment called C3a serves to increase vascular permeability and promote extravasatisation of phagocytes, while the larger C3b fragment can be used as an opsonin or bind to either type of C3 convertase to form the trimolecular C5 convertase to activate C5 for the membrane attack complex.
  • Since C3 convertases cleave C3 to produce C3b which can then form an additional C3 convertase through the alternative pathway, this is a potential mechanism of signal amplification in the complement cascade resulting in the deposition of large numbers of C3b molecules on the surface of activating particles, enabling opsonisation and acute local inflammation.