A positive regulator of the alternate pathway (AP) of complement (PubMed:16301317, PubMed:20382442, PubMed:28264884, PubMed:9748277). It binds to and stabilizes the C3- and C5-convertase enzyme complexes (PubMed:16301317, PubMed:20382442, PubMed:28264884, PubMed:9748277). Inhibits CFI-CFH mediated degradation of Complement C3 beta chain (C3b) (PubMed:31507604). {ECO:0000269|PubMed:16301317, ECO:0000269|PubMed:20382442, ECO:0000269|PubMed:28264884, ECO:0000269|PubMed:31507604, ECO:0000269|PubMed:9748277}. This is the function of ENSG00000126759 (CFP, complement factor properdin).