3.4.21.47	marked stabilization of enzyme by naturally occuring IgG directed against the enzyme. Antibody prevents convertase decay in the presence of factor H. In addition, the antibody stabilizes enzyme precursors and promotes enzyme assembly	670292	
3.4.21.47	properdin stabilizes enzyme-IgG complexes before any other complement protein has bound to them. The alternative pathway of convertase generation may depend on whether properdin is bound to its precursor, a C3b or a C3b2-IgG complex	649689	
3.4.21.47	the C3 convertase is stabilized by the binding of properdin	707849	
3.4.21.47	the enzyme has a very short half-life. Dissociation of the two noncovalently bound subunits proceeds with a half-life of 1-3 min at 37°C under physiological conditions, and this rate increases greatly if regulatory proteins are present. Numerous decay-accelerating proteins are present in plasma and on host cells that bind to the noncatalytic subunit C3b and increase the rate at which the catalytic subunit Bb is released into the medium. Bb loses its enzymatic activity and its ability to bind to C3b upon release. Although C3b is able to rebind Bb and reform the enzyme, the interaction with most decay-accelerating factors also leads to permanent proteolytic interaction of the cell-bound subunit C3b by a fluid-phase protease Factor I. These regulatory events limit cleavage of C3, reduce release of the anaphylatoxin C3a and control the formation of more efficient C5 convertase enzymes	649815	
3.4.21.47	the enzyme is subject to irreversible dissociation by three proteins: DAF, CR1 and factor H	652225