ENZYME entry: EC 6.5.1.8

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)
Cofactor(s)
Mn(2+).
Comment(s)
  • 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.
Cross-references
BRENDA6.5.1.8
EC2PDB6.5.1.8
ExplorEnz6.5.1.8
PRIAM enzyme-specific profiles6.5.1.8
KEGG Ligand Database for Enzyme Nomenclature6.5.1.8
IUBMB Enzyme Nomenclature6.5.1.8
IntEnz6.5.1.8
MEDLINEFind literature relating to 6.5.1.8
MetaCyc6.5.1.8

View entry in original ENZYME format
View entry in raw text format (no links)
All ENZYME / UniProtKB/Swiss-Prot entries corresponding to 6.5.1.-
All ENZYME / UniProtKB/Swiss-Prot entries corresponding to 6.5.-.-
All ENZYME / UniProtKB/Swiss-Prot entries corresponding to 6.-.-.-