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. Protein modification; protein ubiquitination. The APC/C is composed of at least 13 subunits that stay tightly associated throughout the cell cycle: APC1, APC2, APC4, APC5, APC9, APC11, CDC16, CDC23, CDC26, CDC27, DOC1, MND2 and SWM1. CDC26 is required to tether the essential subunits APC9, CDC27 and CDC16 to the complex. Belongs to the CDC26 family. Was originally thought to be a suppressor of CDC26.