Reaction catalyzed by N-terminal E2 ubiquitin-conjugating enzyme (2.3.2.25)

	[ubiquitin-carrier protein Ubc16]-S-ubiquitinyl-L-cysteine	+		[SUMO-2]-NH2	=		[ubiquitin-carrier protein Ubc16]-L-cysteine	+		N-terminal-ubiquitinyl-[SUMO-2]
	[ubiquitin-carrier protein Ubc16]-S-ubiquitinyl-L-cysteine	+		[SUMO-2]-NH2	=		[ubiquitin-carrier protein Ubc16]-L-cysteine	+		N-terminal-ubiquitinyl-[SUMO-2]