Component of the anaphase promoting complex/cyclosome (APC/C); a cell cycle-regulated E3 ubiquitin-protein ligase complex that controls progression through mitosis and the G1 phase of the cell cycle. The APC/C is thought to confer substrate specificity and; in the presence of ubiquitin-conjugating E2 enzymes; it catalyzes the formation of protein-ubiquitin conjugates that are subsequently degraded by the 26S proteasome. In early mitosis; the APC/C is activated by CDC20 and targets securin PDS1; the B-type cyclin CLB5; and other anaphase inhibitory proteins for proteolysis; thereby triggering the separation of sister chromatids at the metaphase-to-anaphase transition. In late mitosis and in G1; degradation of CLB5 allows activation of the APC/C by CDH1; which is needed to destroy CDC20 and the B-type cyclin CLB2 to allow exit from mitosis and creating the low CDK state necessary for cytokinesis and for reforming prereplicative complexes in G1 prior to another round of replication. {ECO:0000269|PubMed:10871279; ECO:0000269|PubMed:12413490; ECO:0000269|PubMed:12609981; ECO:0000269|PubMed:7925276; ECO:0000269|PubMed:8423787}.