Reaction catalyzed by (E3-independent) E2 ubiquitin-conjugating enzyme (2.3.2.24)

	[(E3-independent) E2 ubiquitin-conjugating E2 enzyme]-S-monoubiquitinyl-L-cysteine	+		[acceptor protein]-L-lysine	=		[(E3-independent) E2 ubiquitin-conjugating enzyme]-L-cysteine	+		[acceptor protein]-N6-monoubiquitinyl-L-lysine
	[(E3-independent) E2 ubiquitin-conjugating E2 enzyme]-S-monoubiquitinyl-L-cysteine	+		[acceptor protein]-L-lysine	=		[(E3-independent) E2 ubiquitin-conjugating enzyme]-L-cysteine	+		[acceptor protein]-N6-monoubiquitinyl-L-lysine