title: Crystallographic and spectroscopic snapshots reveal a dehydrogenase in action.
abstract: Aldehydes are ubiquitous intermediates in metabolic pathways and their innate reactivity can often make them quite unstable. There are several aldehydic intermediates in the metabolic pathway for tryptophan degradation that can decay into neuroactive compounds that have been associated with numerous neurological diseases. An enzyme of this pathway, 2-aminomuconate-6-semialdehyde dehydrogenase, is responsible for 'disarming' the final aldehydic intermediate. Here we show the crystal structures of a bacterial analogue enzyme in five catalytically relevant forms: resting state, one binary and two ternary complexes, and a covalent, thioacyl intermediate. We also report the crystal structures of a tetrahedral, thiohemiacetal intermediate, a thioacyl intermediate and an NAD(+)-bound complex from an active site mutant. These covalent intermediates are characterized by single-crystal and solution-state electronic absorption spectroscopy. The crystal structures reveal that the substrate undergoes an E/Z isomerization at the enzyme active site before an sp(3)-to-sp(2) transition during enzyme-mediated oxidation.
authors.affiliation: 1] Department of Chemistry, Georgia State University, Atlanta, Georgia 30303, USA [2] Molecular Basis of Disease Area of Focus Program, Georgia State University, Atlanta, Georgia 30303, USA.
authors.forename: Lu
authors.initials: L
authors.lastname: Huo
authors.affiliation: 1] Department of Chemistry, Georgia State University, Atlanta, Georgia 30303, USA [2] Molecular Basis of Disease Area of Focus Program, Georgia State University, Atlanta, Georgia 30303, USA.
authors.forename: Ian
authors.initials: I
authors.lastname: Davis
authors.affiliation: Department of Chemistry, Georgia State University, Atlanta, Georgia 30303, USA.
authors.forename: Fange
authors.initials: F
authors.lastname: Liu
authors.affiliation: Photon Sciences Directorate, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Babak
authors.initials: B
authors.lastname: Andi
authors.affiliation: 1] Department of Chemistry, Georgia State University, Atlanta, Georgia 30303, USA [2] Molecular Basis of Disease Area of Focus Program, Georgia State University, Atlanta, Georgia 30303, USA.
authors.forename: Shingo
authors.initials: S
authors.lastname: Esaki
authors.affiliation: Department of Life Science and Biotechnology and ORDIST, Kansai University, Suita, Osaka 564-8680, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Iwaki
authors.affiliation: Department of Life Science and Biotechnology and ORDIST, Kansai University, Suita, Osaka 564-8680, Japan.
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Hasegawa
authors.affiliation: 1] Photon Sciences Directorate, Brookhaven National Laboratory, Upton, New York 11973, USA [2] Biosciences Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Allen M
authors.initials: AM
authors.lastname: Orville
authors.affiliation: 1] Department of Chemistry, Georgia State University, Atlanta, Georgia 30303, USA [2] Molecular Basis of Disease Area of Focus Program, Georgia State University, Atlanta, Georgia 30303, USA.
authors.forename: Aimin
authors.initials: A
authors.lastname: Liu
mesh_terms: D000447:Aldehydes / Q000378:metabolism*; D050648:Aminomuconate-Semialdehyde Dehydrogenase / Q000737:chemistry* / Q000378:metabolism; D019295:Computational Biology; D003461:Crystallography; D007700:Kinetics; D013058:Mass Spectrometry; D008958:Models, Molecular; D011487:Protein Conformation; D011551:Pseudomonas fluorescens / Q000201:enzymology*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D000447:Aldehydes; D050648:Aminomuconate-Semialdehyde Dehydrogenase