Structure of inorganic pyrophosphatase from Helicobacter pylori

Inorganic pyrophosphatase (PPase) is a ubiquitous cytosolic enzyme which catalyzes the hydrolysis of inorganic pyrophosphate (PP_i) to orthophosphate (P_i). The crystal structure of inorganic pyrophosphatase from Helicobacter pylori (H-­PPase) has been solved by MAD and refined to an R factor of 20.6% at 2.6 Å resolution. The crystallographic asymmetric unit contains a homohexameric H-PPase arranged as a dimer of trimers. While most of the structural elements of PPases are highly conserved in H-PPase, some unique structural features are localized in the flexible loops near the active site, suggesting that the structural flexibility of these loops is required for the catalytic efficiency of PPase.