3.5.4.13	Ca2+	-	209519	
3.5.4.13	Ca2+	can partially substitute for Mg2+	688732	
3.5.4.13	Co2+	-	209518, 209519	
3.5.4.13	Mg2+	-	209518, 209519, 209520, 209521, 684700, 686667	
3.5.4.13	Mg2+	absolutely required	652395	
3.5.4.13	Mg2+	the enzyme depends on divalent cations, Mg2+ is preferred , but can partially be substituted by Ca2+, Ni2+, or Mn2+	688732	
3.5.4.13	Mn2+	-	209518, 209519	
3.5.4.13	Mn2+	can partially substitute for Mg2+	688732	
3.5.4.13	Ni2+	can partially substitute for Mg2+	688732	
3.5.4.13	Zn2+	the enzyme contains a zinc binding site, but shows less than 6% of maximal activity with Zn2+ as divalent cation	688732