Activator protein that regulates the ubiquitin ligase activity and substrate specificity of the anaphase promoting complex/cyclosome (APC/C). Protein modification; protein ubiquitination. Associates with the APC/C complex. Interacts with CDC20-1, CDC20-2, CYCA1-1, CYCA3-4, CYCB1-1 AND CYCB1-2. Binds to GIG1 and PYM. Expressed during G2/M and M phases. FZR2 controls the induction of early rounds of endoreduplication while the remaining rounds may be mediated by FZR1 and FZR3. Belongs to the WD repeat CDC20/Fizzy family.