Ubiquitin conjugating enzymes in the regulation of the autophagy-dependent degradation pathway

•Ubiquitin regulates two major degradation systems in mammalian cells, depending on proteasomes or autophagy-lysosomes.•Sequential reactions of enzymes, E1, E2 and E3 are key in ubiquitination.•Roles of previously unappreciated ubiquitin conjugating enzymes (E2s) in autophagy are emerging.•This review describes about biochemical properties of E2s, and those regulating autophagy in different manners.