Required for full ubiquitin ligase activity of the anaphase promoting complex/cyclosome (APC/C) and may confer substrate specificity upon the complex. Is regulated by MAD2L1: in metaphase the MAD2L1-CDC20-APC/C ternary complex is inactive and in anaphase the CDC20-APC/C binary complex is active in degrading substrates. The CDC20-APC/C complex positively regulates the formation of synaptic vesicle clustering at active zone to the presynaptic membrane in postmitotic neurons. CDC20-APC/C-induced degradation of NEUROD2 induces presynaptic differentiation. Protein modification; protein ubiquitination. Component of a complex with CDC20, CDC27, SPATC1 and TUBG1 (PubMed:15280373). Interacts with NEUROD2 (PubMed:19900895). Interacts with dimeric MAD2L1 in its closed conformation form (By similarity). Interacts with BUB1B (By similarity). The phosphorylated form interacts with APC/C (By similarity). Interacts with NINL (By similarity). May interact with MAD2L2 (By similarity). Interacts with CDK5RAP2 (By similarity). Interacts with SIRT2 (PubMed:22014574). Interacts with isoform 1 of NEK2 (By similarity). Interacts with HSF1 (via phosphorylated form); this interaction occurs in mitosis in a MAD2L1-dependent manner and prevents PLK1-stimulated degradation of HSF1 by blocking the recruitment of the SCF(BTRC) ubiquitin ligase complex (By similarity). Interacts (via the N-terminal substrate-binding domain) with FBXO5 (PubMed:15526037). Interacts with CCNF (By similarity). Acetylated. Deacetylated at Lys-66 by SIRT2; deacetylation enhances the interaction of CDC20 with CDC27, leading to activation of anaphase promoting complex/cyclosome (APC/C). Phosphorylated during mitosis, probably by maturation promoting factor (MPF). Phosphorylated by BUB1 at Ser-41; Ser-72; Ser-92; Ser-153; Thr-157 and Ser-161. Phosphorylated by NEK2 (By similarity). Dephosphorylated by CTDP1. Ubiquitinated and degraded by the proteasome during spindle assembly checkpoint. Ubiquitinated at Lys-490 during prometaphase. Ubiquitination at Lys-485 and Lys-490 has no effect on its ability to bind the APC/C complex (By similarity). Belongs to the WD repeat CDC20/Fizzy family.