Abstract:Uncovering the comprehensive catalytic mechanism for the activation of triplet O2 through metal-free and cofactor-free oxidases and oxygenases remains one of the most challenging questions in the area of enzymatic...
“…Given the resemblance of AlpJ-family oxygenases to cofactorindependent anthrone oxygenases rather than to the conven-tional FADH 2 -dependent counterparts, we aimed to investigate the potential for catalyzing oxidation reactions in a cofactorindependent manner. For cofactor-independent oxygenases such as TcmH and ActVA-Orf6, the substrates were able to reductively activate molecular oxygen, thereby enabling subsequent oxidation reactions [21][22][23][24]. However, in the documented reactions of AlpJ-family oxygenases, the substrate 1 appeared insufficient in providing the requisite reducing power, considering the quinone structure.…”
Section: Resultsmentioning
confidence: 99%
“…There are many reported cofactor-independent oxygenases, including anthrone oxygenases such as ActVA-Orf6 and nogalamycin monooxygenase (NMO or SnoaB) [21,23,[29][30][31][32], TnmJ and TnmK2 [24], 1-H-3-hydroxy-4-oxoquinaldine-2,4dioxygenase (HOD) [33,34], and urate oxidase [35,36]. Investigations into NMO and HOD revealed the utilization of substrates to activate molecular oxygen, leading to the generation of a substrate radical and the superoxide anion O 2 •− [29,33,37].…”
Section: Inhibition Of Cofactor-independent Catalytic Activities Of A...mentioning
Biosynthesis of atypical angucyclines involves unique oxidative B-ring cleavage and rearrangement reactions, which are catalyzed by AlpJ-family oxygenases, including AlpJ, JadG, and GilOII. Prior investigations established the essential requirement for FADH2/FMNH2 as cofactors when utilizing the quinone intermediate dehydrorabelomycin as a substrate. In this study, we unveil a previously unrecognized facet of these enzymes as cofactor-independent oxygenases when employing the hydroquinone intermediate CR1 as a substrate. The enzymes autonomously drive oxidative ring cleavage and rearrangement reactions of CR1, yielding products identical to those observed in cofactor-dependent reactions of AlpJ-family oxygenases. Furthermore, the AlpJ- and JadG-catalyzed reactions of CR1 could be quenched by superoxide dismutase, supporting a catalytic mechanism wherein the substrate CR1 reductively activates molecular oxygen, generating a substrate radical and the superoxide anion O2•−. Our findings illuminate a substrate-controlled catalytic mechanism of AlpJ-family oxygenases, expanding the realm of cofactor-independent oxygenases. Notably, AlpJ-family oxygenases stand as a pioneering example of enzymes capable of catalyzing oxidative reactions in either an FADH2/FMNH2-dependent or cofactor-independent manner.
“…Given the resemblance of AlpJ-family oxygenases to cofactorindependent anthrone oxygenases rather than to the conven-tional FADH 2 -dependent counterparts, we aimed to investigate the potential for catalyzing oxidation reactions in a cofactorindependent manner. For cofactor-independent oxygenases such as TcmH and ActVA-Orf6, the substrates were able to reductively activate molecular oxygen, thereby enabling subsequent oxidation reactions [21][22][23][24]. However, in the documented reactions of AlpJ-family oxygenases, the substrate 1 appeared insufficient in providing the requisite reducing power, considering the quinone structure.…”
Section: Resultsmentioning
confidence: 99%
“…There are many reported cofactor-independent oxygenases, including anthrone oxygenases such as ActVA-Orf6 and nogalamycin monooxygenase (NMO or SnoaB) [21,23,[29][30][31][32], TnmJ and TnmK2 [24], 1-H-3-hydroxy-4-oxoquinaldine-2,4dioxygenase (HOD) [33,34], and urate oxidase [35,36]. Investigations into NMO and HOD revealed the utilization of substrates to activate molecular oxygen, leading to the generation of a substrate radical and the superoxide anion O 2 •− [29,33,37].…”
Section: Inhibition Of Cofactor-independent Catalytic Activities Of A...mentioning
Biosynthesis of atypical angucyclines involves unique oxidative B-ring cleavage and rearrangement reactions, which are catalyzed by AlpJ-family oxygenases, including AlpJ, JadG, and GilOII. Prior investigations established the essential requirement for FADH2/FMNH2 as cofactors when utilizing the quinone intermediate dehydrorabelomycin as a substrate. In this study, we unveil a previously unrecognized facet of these enzymes as cofactor-independent oxygenases when employing the hydroquinone intermediate CR1 as a substrate. The enzymes autonomously drive oxidative ring cleavage and rearrangement reactions of CR1, yielding products identical to those observed in cofactor-dependent reactions of AlpJ-family oxygenases. Furthermore, the AlpJ- and JadG-catalyzed reactions of CR1 could be quenched by superoxide dismutase, supporting a catalytic mechanism wherein the substrate CR1 reductively activates molecular oxygen, generating a substrate radical and the superoxide anion O2•−. Our findings illuminate a substrate-controlled catalytic mechanism of AlpJ-family oxygenases, expanding the realm of cofactor-independent oxygenases. Notably, AlpJ-family oxygenases stand as a pioneering example of enzymes capable of catalyzing oxidative reactions in either an FADH2/FMNH2-dependent or cofactor-independent manner.
“…Herein, we have theoretically studied the selected reaction by using DFT, which has been widely applied for confirming the possible mechanisms of organocatalytic, − organometallic, − and enzyme , reactions. Gaussian 09 software was employed to perform all of the calculations in this work.…”
Organocatalytic
desymmetrization reaction is a powerful tool for
constructing axial chirality, but the theoretical study on the origin
of stereoselectivity still lags behind even now. In this work, the
N-heterocyclic carbene (NHC)-catalyzed desymmetrization reaction of
biaryl frameworks for the synthesis of axially chiral aldehydes has
been selected and theoretically investigated by using density functional
theory (DFT). The fundamental pathway involves several steps, i.e.,
desymmetrization, formation of Breslow oxidation, esterification,
and NHC regeneration. The desymmetrization and formation of Breslow
processes have been identified as stereoselectivity-determining and
rate-determining steps. Further weak interaction analyses proved that
the C–H···O hydrogen bond and C–H···π
interactions are responsible for the stability of the key stereoselective
desymmetrization transition states. This research contributes to understanding
the nature of NHC-catalyzed desymmetrization reactions for the synthesis
of axially chiral compounds.
“…(3) What are the roles of residues in the active pocket of HHDHamb? These issues and our interest in enzyme catalysis research studies − prompt us to carry out this work. This computational work could provide necessary guidance for the rational design of an HHDHamb-catalyzed epoxide ring-opening reaction with special chemoselectivity. 2 Possible Chemoselective Pathways of the HHDHamb-Catalyzed Ring-Opening Reaction of Epoxide with NO 2 − …”
By performing molecular dynamics
(MD), quantum mechanical/molecular
mechanical (QM/MM) calculations, and QM cluster calculations, the
origin of chemoselectivity of halohydrin dehalogenase (HHDH)-catalyzed
ring-opening reactions of epoxide with the nucleophilic reagent NO2
− has been explored. Four possible chemoselective
pathways were considered, and the computed results indicate that the
pathway associated with the nucleophilic attack on the Cα position
of epoxide by NO2
− is most energetically
favorable and has an energy barrier of 12.9 kcal/mol, which is close
to 14.1 kcal/mol derived from experimental kinetic data. A hydrogen
bonding network formed by residues Ser140, Tyr153, and Arg157 can
strengthen the electrophilicity of the active site of the epoxide
substrate to affect chemoselectivity. To predict the energy barrier
trends of the chemoselective transition states, multiple analyses
including distortion analysis and electrophilic Parr function (P
k
+) analysis were carried out with
or without an enzyme environment. The obtained insights should be
valuable for the rational design of enzyme-catalyzed and biomimetic
organocatalytic epoxide ring-opening reactions with special chemoselectivity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
