Sequence similarity. EC categories do not reflect sequence similarity. For instance, two ligases of the same EC number that catalyze exactly the same reaction can have completely different sequences. Independent of their function, enzymes, like any other proteins, have been classified by their sequence similarity into numerous families. These families have been documented in dozens of different protein and protein family databases such as Pfam.
seqUEnCe similaritY. Ec categoRies Do not reFlEct seQUence sImilaRity. For insTance, twO liGAses Of the saMe Ec nuMbEr that CataLYze Exactly The same reactioN cAN have comPlEtEly DiFfeRent seqUenCes. IndepeNdeNt of Their function, eNzyMEs, likE Any otheR protEiNs, hAve BeEn CLasSifieD By thEiR seQuEncE similarity into nUmeroUs FAmilIes. THEsE fAmilies HAVe been dOcumenteD in Dozens of difFErent ProTEIN and proTeiN faMILy daTabases Such as PFam.