Crystallographic Trapping of Reaction Intermediates in Quinolinic Acid Synthesis by NadA.
Volbeda, A., Saez Cabodevilla, J., Darnault, C., Gigarel, O., Han, T.H., Renoux, O., Hamelin, O., Ollagnier-de-Choudens, S., Amara, P., Fontecilla-Camps, J.C.(2018) ACS Chem Biol 13: 1209-1217
- PubMed: 29641168 
- DOI: https://doi.org/10.1021/acschembio.7b01104
- Primary Citation of Related Structures:  
6F48, 6F4D, 6F4L, 6G74 - PubMed Abstract: 
NadA is a multifunctional enzyme that condenses dihydroxyacetone phosphate (DHAP) with iminoaspartate (IA) to generate quinolinic acid (QA), the universal precursor of the nicotinamide adenine dinucleotide (NAD(P)) cofactor. Using X-ray crystallography, we have (i) characterized two of the reaction intermediates of QA synthesis using a "pH-shift" approach and a slowly reacting Thermotoga maritima NadA variant and (ii) observed the QA product, resulting from the degradation of an intermediate analogue, bound close to the entrance of a long tunnel leading to the solvent medium. We have also used molecular docking to propose a condensation mechanism between DHAP and IA based on two previously published Pyrococcus horikoshi NadA structures. The combination of reported data and our new results provide a structure-based complete catalytic sequence of QA synthesis by NadA.
Organizational Affiliation: 
Univ. Grenoble Alpes, CEA , CNRS, IBS, Metalloproteins Unit , F-38000 Grenoble , France.