Parkinson's disease is frequently caused by mutations in the genes encoding PINK1 and parkin, which together mediate the selective degradation of mitochondrial proteins and whole organelles by autophagy – a process known as mitophagy. Parkin is a E3 ubiquitin ligase that is recruited to mitochondria by the mitochondrial kinase PINK1. However, the E2 co-enzymes that are necessary for parkin activation and subsequent mitophagy have not been investigated thoroughly. On page 3488, Wolfdieter Springer and colleagues screen 11 (out of the total 35) human active E2 enzymes that they have previously characterised for a role in parkin activation, using an unbiased high content imaging small interfering RNA approach. They describe here a number of E2 enzymes that regulate different steps of parkin activity at mitochondria. UBE2D family members and UBE2L3 are involved in the initial activation of parkin and its translocation to mitochondria by charging parkin with ubiquitin. UBE2N also cooperates with parkin, but through a different mechanism; it facilitates the clustering of damaged mitochondria. By contrast, UBE2R1 negatively affects parkin activity as its depletion results in increased parkin translocation to mitochondria and recruitment of the autophagy adaptor p62. Thus, these results suggest that activation and function of the E3 ligase of parkin is regulated differently by different E2 enzymes, which could have important implications for the pathogenesis of Parkinson's disease.