Crystal structure of a thermophilic family II inorganic pyrophosphatase enabling high-temperature adaptation in Thermodesulfobacterium commune

Inorganic pyrophosphatases (PPases) are crucial for energy metabolism and classified into families with distinct metal ion requirements and structural features. This study is the first to successfully express, purify, and structurally characterize a thermophilic family II PPase isolated from Thermodesulfobacterium commune ( Tc PPase). Tc PPase, which is optimally activated by Co ²⁺ and Mn ²⁺ , required both the N- and C-terminal domains for complete catalytic function. Comparative structural analyses of psychrophilic and mesophilic homologs revealed that the enhanced thermal stability of Tc PPase was due to its strong hydrophobic interactions, high proline content, dense hydrogen bond network, and additional salt bridges. These findings reveal the molecular basis for the thermal adaptation of family II PPases, providing valuable insights for thermostable enzyme engineering for biotechnological applications.