The function of CDC20 (cell division cycle 20, ENSG00000117399) is as follows. Substrate-specific adapter and activator of the anaphase promoting complex/cyclosome (APC/C) that confers substrate specificity by binding to substrates and targeting them to the APC/C for ubiquitination and degradation (PubMed:9734353, PubMed:27030811, PubMed:29343641, PubMed:27120157, PubMed:27509861). Essential for activating APC/C in the metaphase/anaphase transition of the cell cycle, targeting the degradation of cyclin B and securin (PubMed:27120157, PubMed:27509861, PubMed:32666501). Recognizes and binds the destruction box (D box), KEB box and ABBA motifs on protein substrates (PubMed:29343641, PubMed:27509861). The CDC20-APC/C complex positively regulates the formation of synaptic vesicle clustering at active zone to the presynaptic membrane in postmitotic neurons (By similarity). CDC20-APC/C-induced degradation of NEUROD2 induces presynaptic differentiation (By similarity). The CDC20-APC/C complex promotes proper dilation formation and radial migration by degrading CCDC41 (By similarity). Component of the mitotic checkpoint complex (MCC), which inhibits APC/C and delays chromosome segregation until all chromosomes are properly attached to the mitotic spindle (PubMed:27509861). The MCC, which consists of CDC20, MAD2L1/MAD2, BUB1B/BUBR1 and BUB3, is a key player of the spindle assembly checkpoint (PubMed:27509861). The MCC-bound APC/C complex is inactive and this delays the metaphase/anaphase transition (PubMed:9811605, PubMed:9637688, PubMed:27509861). When the spindle assembly checkpoint is silenced, the MCC-APC/C complex recruits the E2 enzyme UBCH10 and triggers the auto-ubiquitination of CDC20 in the MCC, thereby reactivating APC/C for transition into anaphase (PubMed:27509861). {ECO:0000250|UniProtKB:Q9JJ66, ECO:0000269|PubMed:27030811, ECO:0000269|PubMed:27120157, ECO:0000269|PubMed:27509861, ECO:0000269|PubMed:29343641, ECO:0000269|PubMed:32666501, ECO:0000269|PubMed:9637688, ECO:0000269|PubMed:9734353, ECO:0000269|PubMed:9811605}.