E2-like enzyme required for the cytoplasm to vacuole transport (Cvt), autophagy and nucleophagy (PubMed:26442587, PubMed:22682742). Acts as an E2-like enzyme that catalyzes the conjugation of ATG12 to ATG5 (PubMed:22682742). ATG12 conjugation to ATG5 is required for proper localization of ATG8 to the preautophagosomal structure (PAS) (By similarity). Likely serves as an ATG5-recognition molecule (By similarity). Forms homooligomers (By similarity). Interacts with ATG10 (PubMed:22682742). Interacts with ATG7 and ATG12 (By similarity). Impairs the formation of preautophagosomal structures (PubMed:26442587). Kluyveromyces marxianus proteins are shorter in length and have a more ordered secondary structure than their S.cerevisiae counterparts, which might contribute to the superior thermotolerance and solubility (PubMed:26442587). K.marxianus could be therefore useful as a new model organism for further elucidation of the molecular details of autophagy (PubMed:26442587). Belongs to the ATG10 family.