EC Explorer

1.1.98.6

ribonucleoside-triphosphate reductase (formate)

ribonucleoside 5′-triphosphate + formate = 2′-deoxyribonucleoside 5′-triphosphate + CO₂ + H₂O

nrdD (gene name), class III ribonucleoside-triphosphate reductase, anaerobic ribonucleotide reductase, anaerobic ribonucleoside-triphosphate reductase

ribonucleoside-5′-triphosphate:formate 2′-oxidoreductase

The enzyme, which is expressed in the bacterium Escherichia coli during anaerobic growth, contains an iron sulfur center. The active form of the enzyme contains an oxygen-sensitive glycyl (1-amino-2-oxoethan-1-yl) radical that is generated by the activating enzyme NrdG via chemistry involving S-adenosylmethionine (SAM) and a [4Fe-4S] cluster. The glycyl radical is involved in generation of a transient thiyl (sulfanyl) radical on a cysteine residue, which attacks the substrate, forming a ribonucleotide 3′-radical, followed by water loss to form a ketyl (α-oxoalkyl) radical. The ketyl radical gains an electron from a cysteine residue and a proton from formic acid, forming 3′-keto-deoxyribonucleotide and generating a thiosulfuranyl (1λ⁴-disulfan-1-yl) radical bridge between methionine and cysteine residues. Oxidation of formate by the thiosulfuranyl radical results in the release of CO₂ and regeneration of the thiyl radical. cf. EC 1.17.4.1, ribonucleoside-diphosphate reductase and EC 1.17.4.2, ribonucleoside-triphosphate reductase (thioredoxin).

created 2017