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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
UniProtKB/Swiss-Prot
B0WCT9, RTCB1_CULQU;  B0EAV2, RTCB1_ENTDS;  C4M244, RTCB1_ENTHI;  
B0XKF3, RTCB2_CULQU;  B0EIW5, RTCB2_ENTDS;  C4M6T2, RTCB2_ENTHI;  
Q17FP1, RTCB_AEDAE;  Q9YB37, RTCB_AERPE;  Q7Q412, RTCB_ANOGA;  
O29399, RTCB_ARCFU;  Q5E9T9, RTCB_BOVIN;  C3YN79, RTCB_BRAFL;  
A8QC60, RTCB_BRUMA;  P90838, RTCB_CAEEL;  A8JC00, RTCB_CHLRE;  
Q6NZS4, RTCB_DANRE;  Q54Y09, RTCB_DICDI;  Q9VIW7, RTCB_DROME;  
P46850, RTCB_ECOLI;  Q9Y3I0, RTCB_HUMAN;  Q4R6X4, RTCB_MACFA;  
Q58095, RTCB_METJA;  Q8TUS2, RTCB_METKA;  Q6LXF9, RTCB_METMP;  
O27634, RTCB_METTH;  C1E9Y5, RTCB_MICCC;  C1MI97, RTCB_MICPC;  
A9UXG6, RTCB_MONBE;  Q99LF4, RTCB_MOUSE;  P59975, RTCB_MYCBO;  
P9WGW4, RTCB_MYCTO;  P9WGW5, RTCB_MYCTU;  Q74MJ0, RTCB_NANEQ;  
A7RKF6, RTCB_NEMVE;  A4S3S3, RTCB_OSTLU;  Q00ZY2, RTCB_OSTTA;  
A9CB42, RTCB_PAPAN;  Q19PY3, RTCB_PIG;  Q4YUZ9, RTCB_PLABA;  
Q8IIU6, RTCB_PLAF7;  B3L4K9, RTCB_PLAKH;  Q7RI54, RTCB_PLAYO;  
Q9V168, RTCB_PYRAB;  Q8ZY09, RTCB_PYRAE;  Q8U0H4, RTCB_PYRFU;  
O59245, RTCB_PYRHO;  Q6AYT3, RTCB_RAT;  B8LBM8, RTCB_THAPS;  
Q4U923, RTCB_THEAN;  Q5JCZ1, RTCB_THEKO;  Q4N1R8, RTCB_THEPA;  
B3RID0, RTCB_TRIAD;  Q561P3, RTCB_XENTR;  

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