Catalyzes the covalent attachment of ubiquitin to other proteins. May also mediate selective proteolysis pathways. S-ubiquitinyl-[E1 ubiquitin-activating enzyme]-L-cysteine + [E2 ubiquitin-conjugating enzyme]-L-cysteine = [E1 ubiquitin-activating enzyme]-L-cysteine + S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine. Protein modification; protein ubiquitination. Expressed in the conidium during the process of appressorium formation. By hard-surface contact. Ethylene and the host surface wax enhance this induction which is essential for appressorium formation. Belongs to the ubiquitin-conjugating enzyme family.