Ubiquitin pathway for protein degradation
					E1 + ATP + Ub -----------> E1.Ub-AMP + PPi
				E1.Ub-AMP + Ub ----------> E1-s-co-Ub.AMP-Ub
		E1-s-co-Ub.AMP-Ub + E2-SH -----> E2-s-co-Ub + E1.AMP-Ub
	E2-s-co-Ub + Protein-NH2 -------> E2-SH + Protein-NH-CO-Ub