1.1.98.6: ribonucleoside-triphosphate reductase (formate)
This is an abbreviated version!
For detailed information about ribonucleoside-triphosphate reductase (formate), go to the full flat file.
Word Map on EC 1.1.98.6
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1.1.98.6
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glycyl
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s-adenosylmethionine
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formate-lyase
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deoxyribonucleotides
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oxygen-sensitive
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flavodoxins
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adomet
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2,3-aminomutase
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coproporphyrinogen
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radical-based
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thiyl
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homolytic
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benzylsuccinate
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datp-sepharose
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medicine
- 1.1.98.6
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glycyl
- s-adenosylmethionine
- formate-lyase
- deoxyribonucleotides
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oxygen-sensitive
- flavodoxins
- adomet
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2,3-aminomutase
- coproporphyrinogen
-
radical-based
-
thiyl
-
homolytic
- benzylsuccinate
-
datp-sepharose
- medicine
Reaction
Synonyms
anaerobic ribonucleoside-triphosphate reductase, anaerobic ribonucleotide reductase, class III ribonucleoside-triphosphate reductase, nrdD
ECTree
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Substrates Products
Substrates Products on EC 1.1.98.6 - ribonucleoside-triphosphate reductase (formate)
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REACTION DIAGRAM
ribonucleoside 5'-triphosphate + formate
2'-deoxyribonucleoside 5'-triphosphate + CO2 + H2O
CTP + formate
dCTP + CO2 + H2O
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reaction requires both proteins NrdD and NrdG and occurs in two strictly anaerobic steps. During the first step NrdD is activated by S-adenosylmethionine and deazaflavin plus light in a time-dependent reaction. In the second step the actual reduction of CTP by activated NrdD requires dithiothreitol, formate, KCl, and ATP
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2'-deoxyribonucleoside 5'-triphosphate + CO2 + H2O
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ribonucleoside 5'-triphosphate + formate
2'-deoxyribonucleoside 5'-triphosphate + CO2 + H2O
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in its active form, the enzyme contains an iron-sulfur center and an oxygen-sensitive glycyl radical (Gly681). The radical is generated in the inactive protein from S-adenosylmethionine by an auxiliary enzyme system. During catalysis, formate is stoichiometrically oxidized to CO2, and isotope from [3H]formate appears in water
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activation of enzyme involves generation of a specific amino acid free radical that is dependent on a reduced Fe-S cluster and S-adenosylmethionine
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additional information
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reaction with CTP (substrate) and ATP (allosteric effector) in the absence of formate leads to loss of the glycyl radical concomitant with stoichiometric formation of a new radical species and a trapped cytidine derivative that can break down to cytosine. Addition of formate to the new species results in recovery of 80% of the glycly radical and reduction of the cytidine derivative, proposed to be 3'-keto-deoxycytidine, to dCTP and a small amount of cytosine. The structure of the new radical is a thiosulfuranyl [RSSR2] radical, composed of a cysteine thiyl radical stabilized by an interaction with a methionine residue
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additional information
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the enzyme reduces ribonucleotides at a low basal rate. Reduction is stimulated up to 10fold by an appropriate modulator (dGTP for ATP reduction, ATP for CTP and UTP reduction, and dlTP for GTP reduction). The enzyme has one class of sites that binds ATP and dATP and regulates pyrimidine ribonucleotide reduction, and another class that binds dATP, dGTP, and dTTP and regulates purine ribonucleotide reduction
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additional information
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Tequatrovirus T4
no significant UTP reduction under the conditions used
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additional information
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Tequatrovirus T4
the enzyme displays two nucleotide-binding sites. One site exhibits half-maximal saturation at approximately 5 mM 8-azidoadenosine 5'-triphosphate, whereas the other site requires 45 microM. The higher affinity site corresponds to residues 289-291 and the other site to the region to residues 147-160. Photoinsertion of 8-azidoadenosine 5'-triphosphate into the site corresponding to residues 147-160 is almost completely abolished when 100 mM dATP, dGTP, or dTTP is included in the photolabeling reaction mixture, whereas 100 mM ATP, GTP, CTP, or dCTP have virtually no effect
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