Structural and catalytic characterization of the 2,5-dihydroxypyridine ring-cleaving dioxygenase Hpo from Pseudomonas putida S16.

Crystal structure of Hpo from Pseudomonas putida S16 reveals a conserved 2-His-1-carboxylate Fe(II) center and substrate recognition motifs critical for pyridine ring cleavage.

• Why it matters: Pyridine compounds are environmental contaminants that produce toxic intermediates like 2,5-DHP, which require enzymatic detoxification, yet the structural basis of the enzymes involved was previously unknown.
• What they did: The study determined the 2.56 Å crystal structure of Hpo, identified key residues for iron binding and substrate recognition, and used molecular dynamics simulations to confirm their roles in catalysis.
• The result: Findings elucidate the active-site architecture and substrate engagement mechanism of Hpo, advancing understanding of pyridine ring-cleaving dioxygenases and informing environmental detoxification strategies.