C3-convertase

The classical and alternative complement pathways.

There are two forms of C3-convertase (EC 3.4.21.43).

• The first is an enzyme composed of the C4b-C2a complex, which forms during the classical or lectin pathways of the complement system. It is formed when C1s cleaves off a small peptide fragment of C2 C2b from a membrane-bound C4b-C2a 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 into 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 bind to activated bimolecular complex C4b2a to form a trimolecular complex, C5-convertase, which is a specific enzyme for C5.

A convertase (of either type) with an additional 3b (C4b2a3b or C3bBb3b) is known as "C5-convertase".

C3 convertase is, in classical terms, C4b2a; in the 1990s there was a motion put forward to change the nomenclature to C4b2b, however this was unsuccessful.

External links

• MeSH C3+convertase

This hydrolase article is a stub. You can help Wikipedia by expanding it.v · Categories: Hydrolase stubs Complement system EC 3.4.21 Wikimedia Foundation. 2010. Игры ⚽ Нужно сделать НИР? Cerys Matthews Tekapo River Look at other dictionaries: convertase — noun Any of several enzymes that convert a compound into smaller, biologically active compounds …   Wiktionary convertase — Proteases of complement that convert one component into another. See component of complement. * * * con·ver·tase (kən vurґtās) an enzyme that releases an active protein from an inactive precursor, as in the activation of specific… …   Medical dictionary Proprotein convertase 1 — Proprotein convertase subtilisin/kexin type 1 PDB rendering based on 1kn6, the NMR structure of the pro domain …   Wikipedia Proprotein convertase 2 — Proprotein convertase subtilisin/kexin type 2 Identifiers Symbols PCSK2; NEC 2; NEC 2; NEC2; PC2; SPC2 External IDs …   Wikipedia C5-convertase — There are two forms of C5 convertase, both derived from the two C3 convertases. In both cases, the main difference between C3 and C5 convertase is the presence of C3b. Thus, the form derived from the classical complement pathway consists of… …   Wikipedia Proprotein-Convertase 1 — Masse/Länge Primärstruktur 643 Aminosäuren …   Deutsch Wikipedia C3 convertase — an enzyme that splits the complement component C3 to C3a and C3b; the classical pathway C3 convertase is C4b,2a; the alternative pathway C3 convertases are C3b,Bb and C3b,P,Bb; see under complement …   Medical dictionary C5 convertase — an enzyme that splits the complement component C5 to C5a and C5b; the classical pathway C5 convertase is C4b,2a,3b; the alternative pathway C5 convertases are C3bn,Bb and C3bn,P,Bb; see under complement …   Medical dictionary Proprotein convertase — Discovery of Prohormone Convertases = The phenomenon of prohormone conversion was discovered by Donald F. Steiner while examining the biosynthesis of insulin [Steiner DF, Cunningham D, Spigelman L, Aten B 1967 Insulin biosynthesis: evidence for a …   Wikipedia prohormone convertase — pro·hor·mone con·ver·tase (pro horґmōn kən vurґtās) any of a group of serine endopeptidases of the trans Golgi network and secretory vesicles that catalyze the release of an active hormone from an inactive precursor …   Medical dictionary 18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”