EC Explorer

1.17.4.2

ribonucleoside-triphosphate reductase (thioredoxin)

2′-deoxyribonucleoside 5′-triphosphate + thioredoxin disulfide + H₂O = ribonucleoside 5′-triphosphate + thioredoxin

ribonucleotide reductase (ambiguous), 2′-deoxyribonucleoside-triphosphate:oxidized-thioredoxin 2′-oxidoreductase

2′-deoxyribonucleoside-5′-triphosphate:thioredoxin-disulfide 2′-oxidoreductase

9068-66-0

The enzyme, characterized from the bacterium Lactobacillus leichmannii, is similar to class II ribonucleoside-diphosphate reductase (cf. EC 1.17.4.1). However, it is specific for the triphosphate versions of its substrates. The enzyme contains an adenosylcobalamin cofactor that is involved in generation of a transient thiyl (sulfanyl) radical on a cysteine residue. This radical attacks the substrate, forming a ribonucleotide 3′-radical, followed by water loss to form a ketyl (α-oxoalkyl) radical. The ketyl radical is reduced to 3′-keto-deoxynucleotide concomitant with formation of a disulfide anion radical between two cysteine residues. A proton-coupled electron-transfer from the disulfide radical to the substrate generates a 3′-deoxynucleotide radical, and the final product is formed when the hydrogen atom that was initially removed from the 3′-position of the nucleotide by the thiyl radical is returned to the same position. The disulfide bridge is reduced by the action of thioredoxin. cf. EC 1.1.98.6, ribonucleoside-triphosphate reductase (formate).

created 1972, modified 2017