6.2.1.45	ATP + ubiquitin + ubiquitin carrier protein E2	-	AMP + diphosphate + ubiquitin-(ubiquitin carrier protein E2)	-	?	502	
6.2.1.45	ATP + ubiquitin + ubiquitin-fold modifier 1	-	?	-	?	400498	
6.2.1.45	ATP + ubiquitin + Ufm1	-	?	-	?	400499	
6.2.1.45	ATP + ubiquitin + [E1 ubiquitin-activating enzyme]-L-cysteine	-	AMP + diphosphate + S-ubiquitinyl-[E1 ubiquitin-activating enzyme]-L-cysteine	-	?	432709	
6.2.1.45	ATP + ubiquitin + [ubiquitin-activating protein E1]-L-cysteine	-	AMP + diphosphate + [ubiquitin-activating protein E1]-S-ubiquitinyl-L-cysteine	-	?	425987	
6.2.1.45	ATP + ubiquitin + [ubiquitin-activating protein Uba1a]-L-cysteine	-	AMP + diphosphate + [ubiquitin-activating protein Uba1a]-S-ubiquitinyl-L-cysteine	-	?	428404	
6.2.1.45	ATP + ubiquitin + [ubiquitin-activating protein UBE1]-L-cysteine	-	AMP + diphosphate + [ubiquitin-activating protein UBE1]-S-ubiquitinyl-L-cysteine	-	?	428409	
6.2.1.45	ATP + ubiquitin mutant G76A + [ubiquitin-activating protein E1]-L-cysteine	-	AMP + diphosphate + [ubiquitin-activating protein E1]-S-(ubiquitin mutant G76A)yl-L-cysteine	mutant ubiquitin G76A, bearing a Gly to Ala substitution at the COOH terminus is a substrate for El enzyme. Ubiquitin G76A supports PPI-ATP exchange with 500fold decrease in kcat/Km compared to wild-type ubiquitin, does not produce detectable AMP-Ub with native El, produces stoichiometric AMP-Ub with thiol-blocked El, gives a stoichiometric burst of ATP consumption with either native or thiol-blocked El, support El-ubiquitin thiol ester formation with native El, and supports several downstream reactions of the proteolytic pathway with a 20% decrease to the rate of wild type ubiquitin	?	428411	
6.2.1.45	ATP + ubiquitin + [ubiquitin-activating protein E1]-L-cysteine	a carboxylgroup is first activated as an adenylate followed by its direct transfer to an autonomous molecular moiety in a single enzymatic step	AMP + diphosphate + [ubiquitin-activating protein E1]-S-ubiquitinyl-L-cysteine	-	?	425987	
6.2.1.45	additional information	a lysine 48-linked polyubiquitin chain, assembled upon an internal lysine residue of a substrate protein, becomes the principle signal for recognition and target degradation by the 26S proteasome. E1 is not only essential for the initial ATP-dependent activation of ubiquitin in the ubiquitin degradtion pathway, but also capable of the catalytic extension of the polyubiquitin chain on a mono-ubiquitinated substrate	?	-	?	89