2.7.1.44	Co2+	divalent metal ion is required, lower activity than Mg2+ or Mn2+	
2.7.1.44	Mg2+	divalent metal ion is required, Zn2+ or Ni2+ are ineffective	
2.7.1.44	Mg2+	Mn2+ (32% relative activity) and Ca2+ (61% relative activity) can substitute for Mg2+	
2.7.1.44	Mn2+	divalent metal ion is required, higher activity than Mg2+. Zn2+ or Ni2+ are ineffective