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Literature summary for 1.17.98.4 extracted from

  • Khangulov, S.V.; Gladyshev, V.N.; Dismukes, G.C.; Stadtman, T.C.
    Selenium-containing formate dehydrogenase H from Escherichia coli: A molybdopterin enzyme that catalyzes formate oxidation without oxygen transfer (1998), Biochemistry, 37, 3518-3528.
    View publication on PubMed

Metals/Ions

Metals/Ions Comment Organism Structure
Fe oxidation of Mo(IV) centers by the Fe4S4 is used for deprotonation of YH(formate) and transfer of the formate proton H+(formate) against the thermodynamic potential. The Mo-Se bond is estimated to be covalent to the extent of 17-27% of the unpaired electron spin density residing in the valence 4s and 4p selenium orbitals, based on comparison of the scalar and dipolar hyperfine components to atomic 77Se. Two electron oxidation of formate by the Mo(VI) state converts Mo to the reduced Mo(IV) state with the formate proton, H+(formate), transferring to a nearby base Y-. Transfer of one electron to the Fe4S4 center converts Mo(IV) to the EPR detectable Mo(V) state. The Y- is located within magnetic contact to the [Mo-Se] center, as shown by its strong dipolar 1Hf hyperfine couplings. Photolysis of the formate-induced Mo(V) state abolishes the 1Hf hyperfine splitting from YH(formate), suggesting photoisomerization of this group or phototransfer of the proton to a more distant proton acceptor group A-. The minor effect of photolysis on the 77Se-hyperfine interaction with [77Se] selenocysteine suggests that the Y- group is not the Se atom, but instead might be the imidazole ring of the His141 residue which is located in the putative substrate-binding pocket close to the [Mo-Se] center. It is proposed that the transfer of H+(formate) from formate to the active site base Y- is thermodynamically coupled to two-electron oxidation of the formate molecule, thereby facilitating formation of CO2 Escherichia coli
Mo enzyme contains a bis-molybdopterin guanine dinucleotide cofactor. EPR spectroscopy of the Mo(V) state indicates a square pyramidal geometry analogous to that of the Mo(IV) center. The strongest ligand field component is likely the single axial Se atom producing a ground orbital configuration Mo(dxy). The Mo-Se bond is estimated to be covalent to the extent of 17-27% of the unpaired electron spin density residing in the valence 4s and 4p selenium orbitals, based on comparison of the scalar and dipolar hyperfine components to atomic 77Se. Two electron oxidation of formate by the Mo(VI) state converts Mo to the reduced Mo(IV) state with the formate proton, H+(formate), transferring to a nearby base Y-. Transfer of one electron to the Fe4S4 center converts Mo(IV) to the EPR detectable Mo(V) state. The Y- is located within magnetic contact to the [Mo-Se] center, as shown by its strong dipolar 1Hf hyperfine couplings. Photolysis of the formate-induced Mo(V) state abolishes the 1Hf hyperfine splitting from YH(formate), suggesting photoisomerization of this group or phototransfer of the proton to a more distant proton acceptor group A-. The minor effect of photolysis on the 77Se-hyperfine interaction with [77Se] selenocysteine suggests that the Y- group is not the Se atom, but instead might be the imidazole ring of the His141 residue which is located in the putative substrate-binding pocket close to the [Mo-Se] center. It is proposed that the transfer of H+(formate) from formate to the active site base Y- is thermodynamically coupled to two-electron oxidation of the formate molecule, thereby facilitating formation of CO2 Escherichia coli
Se the enzyme contains selenocysteine. The Mo-Se bond is estimated to be covalent to the extent of 17-27% of the unpaired electron spin density residing in the valence 4s and 4p selenium orbitals, based on comparison of the scalar and dipolar hyperfine components to atomic 77Se. Two electron oxidation of formate by the Mo(VI) state converts Mo to the reduced Mo(IV) state with the formate proton, H+(formate), transferring to a nearby base Y-. Transfer of one electron to the Fe4S4 center converts Mo(IV) to the EPR detectable Mo(V) state. The Y- is located within magnetic contact to the [Mo-Se] center, as shown by its strong dipolar 1Hf hyperfine couplings. Photolysis of the formate-induced Mo(V) state abolishes the 1Hf hyperfine splitting from YH(formate), suggesting photoisomerization of this group or phototransfer of the proton to a more distant proton acceptor group A-. The minor effect of photolysis on the 77Se-hyperfine interaction with [77Se] selenocysteine suggests that the Y- group is not the Se atom, but instead might be the imidazole ring of the His141 residue which is located in the putative substrate-binding pocket close to the [Mo-Se] center. It is proposed that the transfer of H+(formate) from formate to the active site base Y- is thermodynamically coupled to two-electron oxidation of the formate molecule, thereby facilitating formation of CO2 Escherichia coli

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
formate + acceptor Escherichia coli the transfer of the formate proton, H+(formate), from formate to the active site base Y- is thermodynamically coupled to two-electron oxidation of the formate molecule, thereby facilitating formation of CO2. Under normal physiological conditions, when electron flow is not limited by the terminal acceptor of electrons, the energy released upon oxidation of Mo(IV) centers by the Fe4S4 is used for deprotonation of YH(formate) and transfer of H+(formate) against the thermodynamic potential. This mechanism of proton release from FDH(Se) may play a physiological role in delivery of the formate proton H+(formate) to hydrogenase 3, which is the natural terminal acceptor of electrons for FDH(Se) CO2 + reduced acceptor
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Organism

Organism UniProt Comment Textmining
Escherichia coli
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-
-

Purification (Commentary)

Purification (Comment) Organism
-
Escherichia coli

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
formate + acceptor the transfer of the formate proton, H+(formate), from formate to the active site base Y- is thermodynamically coupled to two-electron oxidation of the formate molecule, thereby facilitating formation of CO2. Under normal physiological conditions, when electron flow is not limited by the terminal acceptor of electrons, the energy released upon oxidation of Mo(IV) centers by the Fe4S4 is used for deprotonation of YH(formate) and transfer of H+(formate) against the thermodynamic potential. This mechanism of proton release from FDH(Se) may play a physiological role in delivery of the formate proton H+(formate) to hydrogenase 3, which is the natural terminal acceptor of electrons for FDH(Se) Escherichia coli CO2 + reduced acceptor
-
?
formate + benzyl viologen the transfer of the formate proton, H+(formate), from formate to the active site base Y- is thermodynamically coupled to two-electron oxidation of the formate molecule, thereby facilitating formation of CO2. Under normal physiological conditions, when electron flow is not limited by the terminal acceptor of electrons, the energy released upon oxidation of Mo(IV) centers by the Fe4S4 is used for deprotonation of YH(formate) and transfer of H+(formate) against the thermodynamic potential. This mechanism of proton release from FDH(Se) may play a physiological role in delivery of the formate proton H+(formate) to hydrogenase 3, which is the natural terminal acceptor of electrons for FDH(Se) Escherichia coli CO2 + reduced benzyl viologen
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?

Synonyms

Synonyms Comment Organism
formate dehydrogenase H
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Escherichia coli

Cofactor

Cofactor Comment Organism Structure
bis(molybdopterin guanine dinucleotide)molybdenum cofactor
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Escherichia coli