<p>The ATP-grasp superfamily currently includes 17 groups of enzymes, catalyzingATP-dependent ligation of a carboxylate containing molecule to an amino orthiol group-containing molecule [<cite idref="PUB00020972"/>]. They contribute predominantly to macromolecular synthesis. ATP-hydrolysis is used to activate a substrate. For example, DD-ligase transfers phosphate from ATP to D-alanine on the first step of catalysis. On the second step the resulting acylphosphate is attacked by a second D-alanine to produce a DD dipeptide following phosphate elimination [<cite idref="PUB00015340"/>].</p><p>The ATP-grasp domain contains three conserved motifs, corresponding to thephosphate binding loop and the Mg(2+) binding site [<cite idref="PUB00015341"/>]. The fold is characterised by two alpha-beta subdomains that grasp the ATP molecule between them. Each subdomain provides a variable loop that forms a part of the active site, completed by region of other domains not conserved between the various ATP-grasp enzymes [<cite idref="PUB00015342"/>].</p><p>The ATP-grasp domain represented by this entry is found primarily in succinyl-CoA synthetases (<db_xref db="EC" dbkey="6.2.1.5"/>).</p>