Reaction catalyzed by E2 ubiquitin-conjugating enzyme (2.3.2.23)

	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
	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