Figure 5.

Superposition of Ex54 and QPS2 on AMP in hENPP1. AMP has green C atoms, Ex54 has cyan C atons and QPS2 has magenta C atoms. The Zn atoms of the active site are shown as grey spheres and the two water molecules found in the AMP-bound structure but not in the inhibitor-bound structures are shown as red spheres. The methoxy moieties of the inhibitors occupy approximately the same space as that occupied by the two waters in the AMP-bound structure. (a) and (b) show two different orientations to highlight that the fused rings are all in the same plane and that the phosphate moiety of AMP is found in a different orientation to that of the sulfamides of the two inhibitors.