6WPU

Structure of S-allyl-L-cysteine S-oxygenase from Allium sativum

Summary for 6WPU

• Entry DOI: 10.2210/pdb6wpu/pdb
• Descriptor: Flavin-containing monooxygenase, FLAVIN-ADENINE DINUCLEOTIDE, SULFATE ION, ... (4 entities in total)
• Functional Keywords: flavin-containing monooxygenase, flavoprotein, oxidoreductase
• Biological source: Allium sativum (Garlic)
• Total number of polymer chains: 1
• Total formula weight: 53178.44

Authors

Tanner, J.J.,Campbell, A.C.,Schuermann, J.P. (deposition date: 2020-04-27, release date: 2020-06-17, Last modification date: 2024-03-06)

Primary citation

Valentino, H.,Campbell, A.C.,Schuermann, J.P.,Sultana, N.,Nam, H.G.,LeBlanc, S.,Tanner, J.J.,Sobrado, P.
Structure and function of a flavin-dependent S-monooxygenase from garlic (Allium sativum).
J.Biol.Chem., 295:11042-11055, 2020

PubMed Abstract: Allicin is a component of the characteristic smell and flavor of garlic (). A flavin-containing monooxygenase (FMO) produced by (AsFMO) was previously proposed to oxidize -allyl-l-cysteine (SAC) to alliin, an allicin precursor. Here, we present a kinetic and structural characterization of AsFMO that suggests a possible contradiction to this proposal. Results of steady-state kinetic analyses revealed that AsFMO exhibited negligible activity with SAC; however, the enzyme was highly active with l-cysteine, -acetyl-l-cysteine, and allyl mercaptan. We found that allyl mercaptan with NADPH was the preferred substrate-cofactor combination. Rapid-reaction kinetic analyses showed that NADPH binds tightly ( of ∼2 μm) to AsFMO and that the hydride transfer occurs with pro- stereospecificity. We detected the formation of a long-wavelength band when AsFMO was reduced by NADPH, probably representing the formation of a charge-transfer complex. In the absence of substrate, the reduced enzyme, in complex with NADP, reacted with oxygen and formed an intermediate with a spectrum characteristic of C4a-hydroperoxyflavin, which decays several orders of magnitude more slowly than the The presence of substrate enhanced C4a-hydroperoxyflavin formation and, upon hydroxylation, oxidation occurred with a rate constant similar to the The structure of AsFMO complexed with FAD at 2.08-Å resolution features two domains for binding of FAD and NADPH, representative of class B flavin monooxygenases. These biochemical and structural results are consistent with AsFMO being an S-monooxygenase involved in allicin biosynthesis through direct formation of sulfenic acid and not SAC oxidation.

PubMed: 32527723
DOI: 10.1074/jbc.RA120.014484

Experimental method

X-RAY DIFFRACTION (2.084 Å)