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Results 1 - 10 of 23 > >>
EC Number Metals/Ions Commentary Reference
Show all pathways known for 1.17.98.4Display the word mapDisplay the reaction diagram Show all sequences 1.17.98.4Fe each mole of enzyme contains 3.3 gatoms of iron 698686
Show all pathways known for 1.17.98.4Display the word mapDisplay the reaction diagram Show all sequences 1.17.98.4Fe Mo(IV)- and the reduced FeS cluster-containing form of the enzyme is crystallized and this can be converted into Mo(VI)- and oxidized FeS cluster form upon oxidation 698704
Show all pathways known for 1.17.98.4Display the word mapDisplay the reaction diagram Show all sequences 1.17.98.4Fe 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 696191
Show all pathways known for 1.17.98.4Display the word mapDisplay the reaction diagram Show all sequences 1.17.98.4Fe the enzyme may contain one 4Fe-4S cluster 695650
Show all pathways known for 1.17.98.4Display the word mapDisplay the reaction diagram Show all sequences 1.17.98.4Fe the reinterpretation of the crystal structure suggests a new reaction mechanism: In step I, formate binds directly to Mo, displacing Se-Cys140. In step II, the alpha-proton from formate may be transferred to the nearby His141 that acts as general base. In this step the CO2 molecule can be released and two electrons transferred to Mo. Alternatively, step II may involve a selenium-carboxylated intermediate. In step III, electrons from Mo(IV) are transferred via the [4Fe-4S] center to an external electron acceptor and the catalytic cycle is completed 674932
Show all pathways known for 1.17.98.4Display the word mapDisplay the reaction diagram Show all sequences 1.17.98.4Mo contains bis-molybdopterin guanine dinucleotide 695650
Show all pathways known for 1.17.98.4Display the word mapDisplay the reaction diagram Show all sequences 1.17.98.4Mo 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 696191
Show all pathways known for 1.17.98.4Display the word mapDisplay the reaction diagram Show all sequences 1.17.98.4Mo Mo(IV)- and the reduced FeS cluster-containing form of the enzyme is crystallized and this can be converted into Mo(VI)- and oxidized FeS cluster form upon oxidation 698704
Show all pathways known for 1.17.98.4Display the word mapDisplay the reaction diagram Show all sequences 1.17.98.4Mo molybdopterin containg enzyme, Mo is coordinated with the Se atom of selenocysteine 701024
Show all pathways known for 1.17.98.4Display the word mapDisplay the reaction diagram Show all sequences 1.17.98.4Mo the reinterpretation of the crystal structure suggests a new reaction mechanism: In step I, formate binds directly to Mo, displacing Se-Cys140. In step II, the alpha-proton from formate may be transferred to the nearby His141 that acts as general base. In this step the CO2 molecule can be released and two electrons transferred to Mo. Alternatively, step II may involve a selenium-carboxylated intermediate. In step III, electrons from Mo(IV) are transferred via the [4Fe-4S] center to an external electron acceptor and the catalytic cycle is completed 674932
Results 1 - 10 of 23 > >>