C5-convertase
Encyclopedia
C5-convertase is an enzyme involved in the complement system
. Its primary function is to cleave C5
protein to C5a and C5b. C5a is a smaller product and diffuses into the plasma
, whereas C5b remains and initiates the formation of membrane attack complex (MAC).
There are two forms of C5-convertase, one derived from the classical pathway and the other from the alternate pathway. 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 surface bound C4b, C2a, and C3b forming the active C4b2a3b complex, which is the C5 convertase, while the derivation of the alternative complement pathway
consists of two C3b and one Bb and referred to as C3bBbC3b (C5 convertase).
C5 is then converted by either of these into C5a and C5b. C5b complexes with C6 and C7 to settle on the cell surface, serving to recruit C8 to insert into the cell membrane and trigger the binding and polymerization of C9, thus forming the membrane attack complex, which can create a pore in cell membranes in order to kill pathogens.
Complement system
The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism. It is part of the immune system called the innate immune system that is not adaptable and does not change over the course of an individual's lifetime...
. Its primary function is to cleave C5
C5
- Military use :* C-5 Galaxy, a military transport aircraft* C-5 North Star, a 1940s Canadian military aircraft* HMS C5, a 1906 Royal Navy C-class submarine* USS C-5 , a 1908 United States Navy C class submarine...
protein to C5a and C5b. C5a is a smaller product and diffuses into the plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
, whereas C5b remains and initiates the formation of membrane attack complex (MAC).
There are two forms of C5-convertase, one derived from the classical pathway and the other from the alternate pathway. 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
Classical complement pathway
The Classical pathway of activation of the complement system is a group of blood proteins that mediate the specific antibody response. The main activators of the Classical Pathway are antigen-antibody complexes.-Initiation:...
consists of surface bound C4b, C2a, and C3b forming the active C4b2a3b complex, which is the C5 convertase, while the derivation of the alternative complement pathway
Alternative complement pathway
The alternative pathway of the complement system is an innate component of the immune system's natural defense against infections, which can operate without antibody participation....
consists of two C3b and one Bb and referred to as C3bBbC3b (C5 convertase).
C5 is then converted by either of these into C5a and C5b. C5b complexes with C6 and C7 to settle on the cell surface, serving to recruit C8 to insert into the cell membrane and trigger the binding and polymerization of C9, thus forming the membrane attack complex, which can create a pore in cell membranes in order to kill pathogens.