page_title: Aldehyde deformylating oxygenase
section_title: Structure
hierarchical_section_title: Aldehyde deformylating oxygenase / Structure
caption_attribution_description: English: Structure and active site of P marinus cADO in active conformation, PDB 4PGI
context_page_description: Aldehyde deformylating oxygenases are a family of enzymes which catalyze the oxygenation of medium and long chain aldehydes to alkanes via the removal of a carbonyl group as formate.
  n-aldehyde + O₂ + 2 NADPH + H⁺ → -alkane + formate + H₂O + 2 NADP⁺
  Aldehyde deformylating oxygenases are found in cyanobacteria as part of the alkane biosynthesis pathway. Their substrates are medium- to long-chain aldehydes formed from acyl-ACP by acyl-ACP reductases, commonly of 16 and 18 carbons, but potentially as short as nonanal and decanal. Compared to other aldehyde decarbonylases, such as insect or plant aldehyde decarbonylase, cyanobacterial ADO is unusual in evolving formate rather than CO or CO₂ and for residing in the cytosol. It is also enzymatically unusual in catalyzing an formally hydrolytic and redox-neutral oxygenation of the substrate.
context_section_description: Cyanobacterial aldehyde deformylating oxygenases are cytosolic nonheme di-iron oxygenases, but are much smaller (29 kDa) than other members of the family, and share sequence homology with ferritin-like or ribonucleotide reductases. The overall structure is a bundle of 8 alpha-helices coordinating two central iron cofactors via histidine, aspartate and glutamate. The substrate channels lies parallel to the helices and terminates at the di-iron center.
  Conformational changes during the enzymatic cycle of Synechococcus elongates ADO have been observed (PDB: 4QUW​, PDB: 4RC6​, PDB: 4RC7​, PDB: 4RC8​). The binding of the substrate aldehyde displaces two coordinating residues on helix 5 (Glu157 and His160), causing a portion of the helix (residues 144-150) to unwind. The resulting hole in the protein surface exposes the active site, facilitating the entrance of the cosubstrate oxygen.
  A similar conformational change has been observed for Prochlorococcus marinus ADO (PDB: 4PGI​), in which residues 154-165 on helix 5 are unwound in the apoenzyme conformation to facilitate metal entry.
caption: Active conformation of P. marinus cADO (PDB: 4GPI​-A) showing active site coordination.[1]
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