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A new class EC 7, Translocases, has been added to the EC list. It will be part of ENZYME from release 2018_10. Read more about EC 7 here.

ENZYME entry: EC

Accepted Name
3'-phosphate/5'-hydroxy nucleic acid ligase.
Reaction catalysed
  • (Ribonucleotide)(n)-3'-phosphate + 5'-hydroxy-(ribonucleotide)(m) + GTP <=> (ribonucleotide)(n+m) + GMP + diphosphate
  • (Ribonucleotide)(n)-2',3'-cyclophosphate + 5'-hydroxy-(ribonucleotide)(m) + GTP + H(2)O <=> (ribonucleotide)(n+m) + GMP + diphosphate (overall reaction)
  • The enzyme is a 3'-5' nucleic acid ligase with the ability to join RNA with 3'-phosphate or 2',3'-cyclic-phosphate ends to RNA with 5'-hydroxy ends.
  • It can also join DNA with 3'-phosphate ends to DNA with 5'-hydroxy ends, provided the DNA termini are unpaired.
  • The enzyme is found in members of all three kingdoms of life, and is essential in metazoa for the splicing of intron-containing tRNAs.
  • The reaction follows a three-step mechanism with initial activation of the enzyme by GTP hydrolysis, forming a phosphoramide bond between the guanylate and a histidine residue.
  • The guanylate group is transferred to the 3'-phosphate terminus of the substrate, forming the capped structure (DNA/RNA)- 3'-(5'-diphosphoguanosine).
  • When a suitable 5'-OH end is available, the enzyme catalyzes an attack of the 5'-OH on the capped end to form a 3'-5' phosphodiester splice junction, releasing the guanylate.
  • When acting on an RNA 2',3'-cyclic-phosphate, the enzyme cayalyses an additional reaction, hydrolyzing the cyclic phosphate to a 3'-phosphate.
  • The metazoan enzyme requires activating cofactors in order to achieve multiple turnover catalysis.
PRIAM enzyme-specific profiles6.5.1.8
KEGG Ligand Database for Enzyme Nomenclature6.5.1.8
IUBMB Enzyme Nomenclature6.5.1.8
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