Enoate reductases catalyze the reduction of activated C═C bonds with high enantioselectivity. The oxidative half-reaction, which involves the addition of a hydride and a proton to opposite faces of the C═C bond, has been studied for the first time by hybrid quantum mechanics/molecular mechanics (QM/MM). The reduction of 2-cyclohexen-1-one by YqjM from Bacillus subtilis was selected as the model system. Two-dimensional QM/MM (B3LYP-D/OPLS2005) reaction pathways suggest that the hydride and proton are added as distinct steps, with the former step preceding the latter. Furthermore, we present interesting insights into the reactivity of this enzyme, including the weak binding of the substrate in the active site, the role of the two active site histidine residues for polarization of the substrate C═O bond, structural details of the transition states to hydride and proton transfer, and the role of Tyr196 as proton donor. The information presented here will be useful for the future design of enantioselective YqjM mutants for other substrates.
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http://dx.doi.org/10.1021/jacs.5b08687 | DOI Listing |
J Am Chem Soc
January 2025
Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.
A series of Ni complexes bearing a redox and acid-base noninnocent tetraamido macrocyclic ligand, H-(TAML-4) {H-(TAML-4) = 15,15-dimethyl-5,8,13,17-tetrahydro-5,8,13,17-tetraaza-dibenzo[]cyclotridecene-6,7,14,16-tetraone}, with formal oxidation states of Ni, Ni, and Ni were synthesized and characterized structurally and spectroscopically. The X-ray crystallographic analysis of the Ni complexes revealed a square planar geometry, and the [Ni(TAML-4)] complex with the formal oxidation state of Ni was characterized to be [Ni(TAML-4)] with the oxidation state of the Ni ion and the one-electron oxidized TAML-4 ligand, TAML-4. The Ni oxidation state and the TAML-4 radical cation ligand, TAML-4, were supported by X-ray absorption spectroscopy and density functional theory calculations.
View Article and Find Full Text PDFChemistry
January 2025
TU Chemnitz: Technische Universitat Chemnitz, Insitut für Chemie, Straße der Nationen 62, 09111, Chemnitz, GERMANY.
The intramolecular migration of three hydrogen atoms from one moiety of a gaseous radical cation to the other prior to fragmentation is an extremely rare type of redox reaction. Within the scope of this investigation, this scenario requires an ionized but electron-rich arene acceptor bearing a para-(3-hydroxyalkyl) residue. The precise mechanism of such unidirectional 3H transfer processes, including the order of the individual H transfer steps, has remained unclear in spite of previous isotope labelling and recent infrared ion spectroscopy (IRIS) studies.
View Article and Find Full Text PDFBiochim Biophys Acta Bioenerg
January 2025
Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801, USA. Electronic address:
The human mitochondrial nicotinamide nucleotide transhydrogenase (NNT) uses the proton motive force to drive hydride transfer from NADH to NADP and is a major contributor to the generation of mitochondrial NADPH. NNT plays a critical role in maintaining cellular redox balance. NNT-deficiency results in oxidative damage and its absence results in familial glucocorticoid deficiency.
View Article and Find Full Text PDFChemistry
January 2025
University of Oxford, Inorganic Chemistry Laboratory, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND.
Combining experiment and theory, the mechanisms of H2 activation by the potassium-bridged aluminyl dimer K2[Al(NON)]2 (NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tertbutyl-9,9-dimethylxanthene) and its monomeric K+-sequestered counterpart have been investigated. These systems show diverging reactivity towards the activation of dihydrogen, with the dimeric species undergoing formal oxidative addition of H2 at each Al centre under ambient conditions, and the monomer proving to be inert to dihydrogen addition. Noting that this K+ dependence is inconsistent with classical models of single-centre reactivity for carbene-like Al(I) species, we rationalize these observations instead by a cooperative frustrated Lewis pair (FLP)-type mechanism (for the dimer) in which the aluminium centre acts as the Lewis base and the K+ centres as Lewis acids.
View Article and Find Full Text PDFInorg Chem
January 2025
Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan.
Sodium borohydride dihydrate (NaBH·2HO) forms through dihydrogen bonding between the hydridic hydrogen of the BH ion and the protonic hydrogen of the water molecule. High-pressure structural changes in NaBH·2HO, observed up to 11 GPa through X-ray diffraction and Raman scattering spectroscopy, were analyzed to assess the influence of dihydrogen bonds on its crystal structure. At approximately 4.
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