Methyl Transfer Reactivity of Five-Coordinate CH<sub>3</sub>Co<sup>III</sup>Pc

Galezowski, Wlodzimierz

doi:10.1021/ic048698v

Cited by 19 publications

(81 citation statements)

References 75 publications

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“…23 If PMF Odemethylation is catalyzed by the Co-corrinoid system, it would be a demethylase with the largest substrate binding site, because it can metabolize 3,5,7,3′,4′-PMF. Because the Co-corrinoid system is inhibited by cyanide and alkyl iodide, 34,35 KCN and alkyl iodide were added to the cell culture metabolizing 5,7-DMF (Figure 8). All three compounds inhibited the demethylation of 5,7-DMF in a concentration-dependent manner, which strongly suggested that the demethylation of PMFs is catalyzed by a Co-corrinoid enzyme.…”

Section: ■ Discussionmentioning

confidence: 99%

Demethylation of Polymethoxyflavones by Human Gut Bacterium, Blautia sp. MRG-PMF1

Burapan

Kim

Han

2017

J. Agric. Food Chem.

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Polymethoxyflavones (PMFs) were biotransformed to various demethylated metabolites in the human intestine by the PMF-metabolizing bacterium, Blautia sp. MRG-PMF1. Because the newly formed metabolites can have different biological activities, the pathways and regioselectivity of PMF bioconversion were investigated. Using an anaerobic in vitro study, 12 PMFs, 5,7-dimethoxyflavone (5,7-DMF), 5-hydroxy-7-methoxyflavone (5-OH-7-MF), 3,5,7-trimethoxyflavone (3,5,7-TMF), 5-hydroxy-3,7-dimethoxyflavone (5-OH-3,7-DMF), 5,7,4'-trimethoxyflavone (5,7,4'-TMF), 5-hydroxy-7,4'-dimethoxyflavone (5-OH-7,4'-DMF), 3,5,7,4'-tetramethoxyflavone (3,5,7,4'-TMF), 5-hydroxy-3,7,4'-trimethoxyflavone (5-OH-3,7,4'-TMF), 5,7,3',4'-tetramethoxyflavone (5,7,3',4'-TMF), 3,5,7,3',4'-pentamethoxyflavone (3,5,7,3',4'-PMF), 5-hydroxy-3,7,3',4'-tetramethoxyflavone (5-OH-3,7,3',4'-TMF), and 5,3'-dihydroxy-3,7,4'-trimethoxyflavone (5,3'-diOH-3,7,4'-TMF), were converted to chrysin, apigenin, galangin, kaempferol, luteolin, and quercetin after complete demethylation. The time-course monitoring of PMF biotransformations elucidated bioconversion pathways, including the identification of metabolic intermediates. As a robust flavonoid demethylase, regioselectivity of PMF demethylation generally followed the order C-7 > C-4' ≈ C-3' > C-5 > C-3. PMF demethylase in the MRG-PMF1 strain was suggested as a Co-corrinoid methyltransferase system, and this was supported by the experiments utilizing other methyl aryl ether substrates and inhibitors.

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Section: ■ Discussionmentioning

confidence: 99%

Demethylation of Polymethoxyflavones by Human Gut Bacterium, Blautia sp. MRG-PMF1

Burapan

Kim

Han

2017

J. Agric. Food Chem.

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“…In order to understand the enzymatic reaction mechanism, it is essential to consider the effects on the electronic and structural properties of the corrin framework as well as the axial ligand. − To evaluate the chemical properties of the corrin framework, two characteristic cobalt corrinoids, di- and tetradehydrocorrin cobalt complexes, have been reported as models of cobalamin . The former cobalt complex is capable of forming a stable Co(III)–C bond similar to that of methylcobalamin.…”

Section: Introductionmentioning

confidence: 99%

“…The latter cobalt complex (Figure b) provides a stable Co(I) species, but the subsequent alkylation reaction does not occur in organic solvents . Furthermore, several substituted cobalamins with substitution at the 10-position of the corrinoid and cobalt corrole derivatives have also been synthesized to investigate the framework effect using theoretical and experimental methods. , In addition to the framework effect, various cobalamin derivatives were synthesized to investigate the axial-ligation effect, particularly the relationship between the Co(III)–C and Co(III)–N bond lengths. ,, A bulky axial ligand such as DMB is known to cause elongation of the Co(III)–C bond due to upward folding of the corrin ring. , This axial ligation generally promotes homolytic cleavage of the Co(III)–C bond as a result of electronic stabilization of the produced Co(II) species. , In contrast, there are few appropriate cobalamin models which replicate the DMB-off/His-on ligation which occurs in the reaction cycle of methionine synthase, where the methyl group bound to the cobalt atom is transferred to homocysteine via the heterolytic Co(III)–C bond cleavage. , To evaluate the effect of the histidine ligation, it is of interest to construct a conjugate model between a cobalt complex and a protein matrix. ,, In our previous work, myoglobin reconstituted with tetradehydrocorrin cobalt(II) complex, rMb(Co II (TDHC)), was prepared to replicate the cobalamin-binding domain of methionine synthase, because the heme pocket of myoglobin possesses a potent histidine (His93) ligand which coordinates to heme in the native protein. The X-ray crystal structure analysis reveals that the His93 residue coordinates to the Co(II) corrinoid, and then reduction of the crystals leads to the tetracoordinated Co(I) corrinoid after deligation of the His93 residue in the heme pocket .…”

Section: Introductionmentioning

confidence: 99%

Crystal Structures and Coordination Behavior of Aqua- and Cyano-Co(III) Tetradehydrocorrins in the Heme Pocket of Myoglobin

et al. 2016

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Myoglobins reconstituted with aqua- and cyano-Co(III) tetradehydrocorrins, rMb(Co(III)(OH2)(TDHC)) and rMb(Co(III)(CN)(TDHC)), respectively, were prepared and investigated as models of a cobalamin-dependent enzyme. The former protein was obtained by oxidation of rMb(Co(II)(TDHC)) with K3[Fe(CN)6]. The cyanide-coordinated Co(III) species in the latter protein was prepared by ligand exchange of rMb(Co(III)(OH2)(TDHC)) with exogenous cyanide upon addition of KCN. The X-ray crystallographic study reveals the hexacoordinated structures of rMb(Co(III)(OH)(TDHC)) and rMb(Co(III)(CN)(TDHC)) at 1.20 and 1.40 Å resolution, respectively. The (13)C NMR chemical shifts of the cyanide in rMb(Co(III)(CN)(TDHC)) were determined to be 108.6 and 110.6 ppm. IR measurements show that the cyanide of rMb(Co(III)(CN)(TDHC)) has a stretching frequency peak at 2151 cm(-1) which is higher than that of cyanocobalamin. The (13)C NMR and IR measurements indicate weaker coordination of the cyanide to Co(III)(TDHC) relative to cobalamin, a vitamin B12 derivative. Thus, the extent of π-back-donation from the cobalt ion to the cyanide ion is lower in rMb(Co(III)(CN)(TDHC)). Furthermore, the pK(1/2) values of rMb(Co(III)(OH2)(TDHC)) and rMb(Co(III)(CN)(TDHC)) were determined by a pH titration experiment to be 3.2 and 5.5, respectively, indicating that the cyanide ligation weakens the Co-N(His93) bond. Theoretical calculations also demonstrate that the axial ligand exchange from water to cyanide elongates the Co-N(axial) bond with a decrease in the bond dissociation energy. Taken together, the cyano-Co(III) tetradehydrocorrin in myoglobin is appropriate for investigation as a structural analogue of methylcobalamin, a key intermediate in methionine synthase reaction.

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“…Furthermore, characteristic imidazolate-like histidine ligation to the cobalamin cofactor is observed in the abovementioned methionine synthase as well as in methylmalonyl-CoA mutase and glutamate mutase [16][17][18][19][20]. Over the past decades, several model systems have been reported using cobalamin and its derivatives as well as cobalt corrinoid complexes [20][21][22][23][24][25][26][27][28]. Previously, our group reported the structure, reactivity and physicochemical properties of myoglobin (Mb) reconstituted with Co(TDHC), (TDHC = 8,12-dicarboxyethyl-1,2,3,7,13,17,18,19-octamethyltetradehydrocorrin), rMb(Co(TDHC)), in efforts to develop a useful proteinbased model of cobalamin-dependent methionine synthase [29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Cobalt tetradehydrocorrins coordinated by imidazolate-like histidine in the heme pocket of horseradish peroxidase

et al. 2017

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Horseradish peroxidase was reconstituted with cobalt tetradehydrocorrin, rHRP(Co(TDHC)), as a structural analog of cobalamin coordinated with an imidazolate-like His residue, which is generally seen in native enzymes. In contrast to the previously reported cobalt tetradehydrocorrin-reconstituted myoglobin, rMb(Co(TDHC)), the HRP matrix was expected to provide strong axial ligation by His170 which has imidazolate character. rHRP(Co(TDHC)) was characterized by EPR and its reaction with reductants indicates a negative shift of its redox potential compared to rMb(Co(TDHC)). Furthermore, aqua- and CN-forms of Co(III) state were prepared. The former species was obtained by oxidation of rHRP(Co(TDHC)) with K[Fe(CN)]. The cyanide-coordinated Co(III) species in the latter was prepared by ligand exchange of rHRP(Co(OH)(TDHC)) with exogenous cyanide upon addition of KCN. The C NMR chemical shift of cyanide in rHRP(Co(CN)(TDHC)) was determined to be 121.8 ppm. IR measurements show that the cyanide of rHRP(Co(CN)(TDHC)) has a stretching frequency peak at 2144 cm. The C NMR and IR measurements indicate strong coordination of cyanide to Co(TDHC) relative to rMb(Co(CN)(TDHC)). Thus, the extent of π-back donation from the cobalt ion to the cyanide ion is relatively high in rHRP(Co(CN)(TDHC)). The pK values of rHRP(Co(OH)(TDHC)) and rHRP(Co(CN)(TDHC)) are the same (pK = 3.2) as determined by a pH titration experiment, indicating that cyanide ligation does not affect Co-His ligation, whereas cyanide ligation weakens the Co-His ligation in rMb(Co(CN)(TDHC)). Taken together, these results indicate that HRP reconstituted with cobalt tetradehydrocorrin is a suitable cobalamin-dependent enzyme model with imidazolate-like His residue.

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Methyl Transfer Reactivity of Five-Coordinate CH₃Co^IIIPc

Cited by 19 publications

References 75 publications

Demethylation of Polymethoxyflavones by Human Gut Bacterium, Blautia sp. MRG-PMF1

Demethylation of Polymethoxyflavones by Human Gut Bacterium, Blautia sp. MRG-PMF1

Crystal Structures and Coordination Behavior of Aqua- and Cyano-Co(III) Tetradehydrocorrins in the Heme Pocket of Myoglobin

Cobalt tetradehydrocorrins coordinated by imidazolate-like histidine in the heme pocket of horseradish peroxidase

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Methyl Transfer Reactivity of Five-Coordinate CH3CoIIIPc

Cited by 19 publications

References 75 publications

Demethylation of Polymethoxyflavones by Human Gut Bacterium, Blautia sp. MRG-PMF1

Demethylation of Polymethoxyflavones by Human Gut Bacterium, Blautia sp. MRG-PMF1

Crystal Structures and Coordination Behavior of Aqua- and Cyano-Co(III) Tetradehydrocorrins in the Heme Pocket of Myoglobin

Cobalt tetradehydrocorrins coordinated by imidazolate-like histidine in the heme pocket of horseradish peroxidase

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Methyl Transfer Reactivity of Five-Coordinate CH₃Co^IIIPc