Electron transfer and reaction mechanism of laccases

Jones, Stephen M.; Solomon, Edward I.

doi:10.1007/s00018-014-1826-6

Cited by 466 publications

(400 citation statements)

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“…2 (SMe) (Im = imidazole, Me = methyl) with Cu(I)/Cu(II) centres. At the BP86/def2-SVP/def2-TZVP(Cu) level, the contribution to the relative redox potential from these thermodynamic corrections is 0.11 V (+0.06 V contribution from the ARP of the small model, see SI).…”

Section: Ferrocene Standard Calibrationmentioning

confidence: 99%

“…These enzymes have been shown, among others, to catalyse the reaction of lignin model compounds to form oxidized radicals. 1,2 As lignin-degrading activity has been related to the oxidative power of these enzymes, their redox potentials are of great fundamental and potentially practical interest. 3 Laccase is a multicopper oxidase (MCO), and represents a special case in the group of the lignindegrading enzymes.…”

Section: Introductionmentioning

confidence: 99%

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Laccase Redox Potentials: pH Dependence and Mutants, a QM/MM Study

Götze

Bühl

2016

J. Phys. Chem. B

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We have studied the T. versicolor laccase T1 site redox potential (RP) at the M06/6-311++G**/SDD(Cu) level of theory, employing QM/MM optimised geometries (RI-BP86/def2-SVP/def2-TZVP(Cu):CHARMM) of the whole protein system with electronic embedding. The oxidation state of the trinuclear cluster was found to affect the T1 site RP by about 0.2-0.3 V, depending on the protein protonation state. The computed laccase RP can be drastically lowered upon introduction of a protonation state corresponding to a neutral environment, by up to -1.37 V, which is likely an overestimation of the effect in vivo. The gradual change of the protonation state by single points without optimisation or equilibration results in a change that is even larger, namely up to about -2.6 V. Thus, the preferred protein conformation supports a high redox potential, compensating for the RP-lowering effect of surface charges. The predicted change in RP on going to the F463M mutant, ca. -0.1 V, is consistent with observations for a related laccase. Based on our results, we also propose and test a D206N mutant, but find it to be locked in a conformation with slightly lower RP.

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Section: Ferrocene Standard Calibrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Laccase Redox Potentials: pH Dependence and Mutants, a QM/MM Study

Götze

Bühl

2016

J. Phys. Chem. B

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“…Among these enzymes laccases (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) uses molecular oxygen to catalyse oxidation of phenolic substrates similar to those found in lignin subunits. A laccase catalysed oxidation cycle involves oxidation of four moles of phenolic substrate and simultaneous reduction of one mole of O2 to H2O [10,11].…”

Section: Introductionmentioning

confidence: 99%

Direct rate assessment of laccase catalysed radical formation in lignin by electron paramagnetic resonance spectroscopy

Munk

Andersen

Meyer

2017

Enzyme and Microbial Technology

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Highlights Time course EPR measurement of direct radical formation by fungal laccases on genuine lignin samples  Assessment of enzyme kinetic rates of radical formation in lignin by two fungal laccases  Identification of different radical formation patterns by a low and high redox potential laccase  Demonstration of different laccase rates on different types of lignin substrates Abstract Laccases (EC 1.10.3.2) catalyse removal of an electron and a proton from phenolic hydroxyl groups, including phenolic hydroxyls in lignins, to form phenoxy radicals during reduction of O2. We employed electron paramagnetic resonance spectroscopy (EPR) for real time measurement of such catalytic radical 2 formation activity on three types of lignin (two types of organosolv lignin, and a lignin rich residue from wheat straw hydrolysis) brought about by two different fungal laccases, derived from Trametes versicolor (Tv) and Myceliophthora thermophila (Mt), respectively. Laccase addition to suspensions of the individual lignin samples produced immediate time and enzyme dose dependent increases in intensity in the EPR signal with g-values in the range 2.0047-2.0050 allowing a direct quantitative monitoring of the radical formation and thus allowed laccase enzyme kinetics assessment on lignin. The experimental data verified that the laccases acted upon the insoluble lignin substrates in the suspensions. When the action on the lignin substrates of the two laccases were compared on equal enzyme dosage levels (by activity units on syringaldazine) the Mt laccase exerted a significantly faster radical formation than the Tv laccase on all three types of lignin substrates. When comparing the equal laccase dose rates on the three lignin substrates the enzymatic radical formation rate on the wheat straw lignin residue was consistently higher than that of the organosolv lignins. The pH-temperature optimum for the radical formation rate in organosolv lignin was determined by response surface methodology to pH 4.8, 33°C and pH 5.8, 33°C for the Tv laccase and the Mt laccase, respectively. The results verify direct radical formation action of fungal laccases on lignin without addition of mediators and the EPR methodology provides a new type of enzyme assay of laccases on lignin.

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“…Cu sites of laccase are divided into three types largely from their features, called type 1 (S-coordinated blue copper), type 2 (normal), and type 3 (O-bridged dinuclear). The type 1 site is found in electron transport chain proteins, with the coordination of cysteine, because they exhibit a blue color due to the strong charge transfer (CT) transitions, also referred to as "blue copper" [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%