5KLK
Crystal structure of 2-aminomuconate 6-semialdehyde dehydrogenase N169D in complex with NAD+ and 2-hydroxymuconate-6-semialdehyde
Summary for 5KLK
| Entry DOI | 10.2210/pdb5klk/pdb |
| Related | 5KLL 5KLM 5KLN 5KLO |
| Descriptor | 2-aminomuconate 6-semialdehyde dehydrogenase, NICOTINAMIDE-ADENINE-DINUCLEOTIDE, (2E,4E)-2-hydroxy-6-oxohexa-2,4-dienoic acid, ... (5 entities in total) |
| Functional Keywords | 2-aminomuconate 6-semialdehyde dehydrogenase, kynurenine pathway, oxidoreductase |
| Biological source | Pseudomonas fluorescens |
| Total number of polymer chains | 4 |
| Total formula weight | 227741.11 |
| Authors | |
| Primary citation | Yang, Y.,Davis, I.,Ha, U.,Wang, Y.,Shin, I.,Liu, A. A Pitcher-and-Catcher Mechanism Drives Endogenous Substrate Isomerization by a Dehydrogenase in Kynurenine Metabolism. J.Biol.Chem., 291:26252-26261, 2016 Cited by PubMed Abstract: Aldehyde dehydrogenase typically performs oxidation of aldehydes to their corresponding carboxylic acid while reducing NAD(P) to NAD(P)H via covalent catalysis mediated by an active-site cysteine residue. One member of this superfamily, the enzyme 2-aminomuconate-6-semialdehyde dehydrogenase (AMSDH), is a component of the kynurenine pathway, which catabolizes tryptophan in mammals and certain bacteria. AMSDH catalyzes the NAD-dependent oxidation of 2-aminomuconate semialdehyde to 2-aminomuconate. We recently determined the first crystal structure of AMSDH and several catalytic cycle intermediates. A conserved asparagine in the oxyanion hole, Asn-169, is found to be H-bonded to substrate-derived intermediates in the active site of AMSDH during catalysis, including both the covalently bound thiohemiacetal and thioacyl intermediates. To better interrogate the significance of the hydrogen bond provided by Asn-169 to the reaction mechanism of AMSDH, we created Ala, Ser, Asp, and Gln mutants and studied them using biochemical, kinetic, crystallographic, and computational studies. The in crystallo chemical reaction of the primary substrate with the co-crystalized complex of the N169D mutant and NAD led to the successful trapping of a new catalytic intermediate that was not previously seen. The structural and computational data are consistent with a substrate imine/enol tautomer intermediate being formed prior to the formation of the covalent bond between the substrate and the active-site cysteine. Thus, AMSDH surprisingly includes an isomerization process within its known catalytic mechanism. These data establish a hidden intrinsic isomerization activity of the dehydrogenase and allow us to propose a pitcher-catcher type of catalytic mechanism for the isomerization. PubMed: 27810899DOI: 10.1074/jbc.M116.759712 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (2.006 Å) |
Structure validation
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