ENZYME entry: EC 1.17.4.2

Accepted Name
Ribonucleoside-triphosphate reductase (thioredoxin).
Alternative Name(s)
Ribonucleotide reductase.
Reaction catalysed
2'-deoxyribonucleoside triphosphate + thioredoxin disulfide + H(2)O <=> ribonucleoside triphosphate + thioredoxin
Cofactor(s)
Adenosylcob(III)alamin.
Comment(s)
  • 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 (alpha-oxoacyl) 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 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.
Cross-references
PROSITEPDOC00665
BRENDA1.17.4.2
EC2PDB1.17.4.2
ExplorEnz1.17.4.2
PRIAM enzyme-specific profiles1.17.4.2
KEGG Ligand Database for Enzyme Nomenclature1.17.4.2
IUBMB Enzyme Nomenclature1.17.4.2
IntEnz1.17.4.2
MEDLINEFind literature relating to 1.17.4.2
MetaCyc1.17.4.2
UniProtKB/Swiss-Prot
Q54CW7, RTPR_DICDI;  Q2PDF6, RTPR_EUGGR;  Q5FMX8, RTPR_LACAC;  
Q03PB4, RTPR_LACBA;  Q1G7W2, RTPR_LACDA;  Q04CQ7, RTPR_LACDB;  
Q041L3, RTPR_LACGA;  A8YW74, RTPR_LACH4;  Q59490, RTPR_LACLE;  
Q035U1, RTPR_LACP3;  A6Q367, RTPR_NITSB;  Q857H2, VG50_BPMB2;  
O64240, VG50_BPMD2;  Q05262, VG50_BPML5;  

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