User:Cboursnell/Sandbox/5 nucleotid

This family includes a 5'-nucleotidase, EC, specific for purines (IMP and GMP). These enzymes are members of the Haloacid Dehalogenase (HAD) superfamily. HAD members are recognised by three short motifs {hhhhDxDx(T/V)}, {hhhh(T/S)}, and either {hhhh(D/E)(D/E)x(3-4)(G/N)} or {hhhh(G/N)(D/E)x(3-4)(D/E)} (where "h" stands for a hydrophobic residue). Crystal structures of many HAD enzymes has verified PSI-PRED predictions of secondary structural elements which show each of the "hhhh" sequences of the motifs as part of beta sheets. This subfamily of enzymes is part of "Subfamily I" of the HAD superfamily by virtue of a "cap" domain in between motifs 1 and 2. This subfamily's cap domain has a different predicted secondary structure than all other known HAD enzymes and thus has been designated "subfamily IG", the domain appears to consist of a mixed alpha/beta fold.