page_title: Nucleotide pyrophosphatase/phosphodiesterase
section_title: Structure
hierarchical_section_title: Nucleotide pyrophosphatase/phosphodiesterase / Structure
caption_attribution_description: English: Schematic of the Xanthomonas axonopodis pv. citri NPP active site in a transition state. Red and blue curved arrows represent nucleophilic addition (AN) and elimination (DN) steps, respectively, of the phosphoryl transfer reaction. These two steps could occur in either order, and probably overlap. The active site's threonine nucleophile is regenerated via hydrolysis. This schematic does not contain any bond length or bond order information. Adapted from Zalatan et al. 2006.
context_page_description: Nucleotide pyrophosphatase/phosphodiesterase is a class of dimeric enzymes that catalyze the hydrolysis of phosphate diester bonds. NPP belongs to the alkaline phosphatase superfamily of enzymes. Humans express seven known NPP isoforms, some of which prefer nucleotide substrates, some of which prefer phospholipid substrates, and others of which prefer substrates that have not yet been determined. In eukaryotes, most NPPs are located in the cell membrane and hydrolyze extracellular phosphate diesters to affect a wide variety of biological processes. Bacterial NPP is thought to localize to the periplasm.
context_section_description: The catalytic site of NPP consists of a two-metal-ion (bimetallo) Zn²⁺ catalytic core. These Zn²⁺ catalytic components are thought to stabilize the transition state of the NPP phosphoryl transfer reaction.
caption: Schematic of Xac NPP active site in a transition state. Violet denotes the phosphodiester substrate. Red and blue curved arrows represent nucleophilic addition (AN) and elimination (DN) steps, respectively, of the phosphoryl transfer reaction. These two steps could occur in either order, and probably overlap. The active site's threonine nucleophile is regenerated via hydrolysis. Adapted from.[1]
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