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Polyphosphate kinase 2 (PPK2) Inorganic polyphosphate (polyP) plays a role in metabolism and regulation and has been proposed to serve as a energy source in a pre-ATP world. In prokaryotes, the synthesis and utilisation of polyP are catalyzed by PPK1, PPK2 and polyphosphatases. Proteins with a single PPK2 domain catalyze polyP-dependent phosphorylation of ADP to ATP, whereas proteins containing 2 fused PPK2 domains phosphorylate AMP to ADP. The structure of PPK2 from Pseudomonas aeruginosa has revealed a a 3-layer alpha/beta/alpha sandwich fold with an alpha-helical lid similar to the structures of microbial thymidylate kinases.
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Jiyao W et al.(2023). "The conserved domain database in 2023.",