9EJ8

Structure of the Lactate Monooxygenase mutant Y44N, Y152F, H290S, T181A, F184P

Summary for 9EJ8

• Entry DOI: 10.2210/pdb9ej8/pdb
• Descriptor: L-lactate 2-monooxygenase, FLAVIN MONONUCLEOTIDE, GLYCEROL, ... (6 entities in total)
• Functional Keywords: alpha-hydroxy acid oxidase, flavoenzyme, lactate metabolism, oxidoreductase
• Biological source: Mycolicibacterium smegmatis
• Total number of polymer chains: 1
• Total formula weight: 44788.94

Authors

Liu, Y.,Sorigue, D.,Jeffrey, P.D.,Hyster, T. (deposition date: 2024-11-27, release date: 2026-02-18)

Primary citation

Liu, Y.,Oblinsky, D.G.,Dell'Orletta, G.,Di Fonte, N.,Sorigue, D.,Page, C.G.,Daidone, I.,Scholes, G.D.,Hyster, T.K.
Photoenzymatic Csp 3 -Csp 3 bond formation via enzyme-templated radical-radical coupling.
Proc.Natl.Acad.Sci.USA, 123:e2529018123-e2529018123, 2026

PubMed Abstract: Cross-couplings are essential reactions in modern chemical synthesis, enabling the rapid construction of complex molecules from simple precursors. Transition metal catalysts are prized for these transformations because their reactivity and selectivity can be tuned via judicious selection of the metal and ligand. Although enzymes offer analogous opportunities for tuning via protein engineering, their application to cross-coupling remains limited, as nature relies on alternative paradigms for building molecular complexity. Here, we report the cross-coupling of alkyl halides and benzylic carboxylic acids using an engineered flavin-dependent lactate monooxygenase-a photoenzyme. The enzyme achieves this feat by exploiting the redox versatility of the flavin cofactor. Stoichiometric experiments, ultrafast spectroscopy, and computational studies support a mechanism in which photoexcited flavin quinone initiates the reaction via oxidative decarboxylation to generate a benzylic radical. The resulting flavin semiquinone can reduce the alkyl halide to form a second organic radical within the protein active site, which rapidly engages in C(sp)-C(sp) bond formation. A variant was engineered to control the stereochemical outcome of this radical-radical coupling event, highlighting the ability of the protein to alter the energetic barrier for a mechanistic step that is traditionally understood to be near barrierless. This work demonstrates that the scope for nonnative reaction mechanisms in biocatalysis far exceeds previously established bounds and has potential to solve a variety of reactivity challenges in cross-coupling chemistry.

PubMed: 41662517
DOI: 10.1073/pnas.2529018123

Experimental method

X-RAY DIFFRACTION (1.42 Å)