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Information on EC 6.5.1.8 - 3'-phosphate/5'-hydroxy nucleic acid ligase

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IUBMB Comments
The enzyme is a GTP- and Mn2+-dependent 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 catalyses 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 catalyses an additional reaction, hydrolysing the cyclic phosphate to a 3'-phosphate . The metazoan enzyme requires activating cofactors in order to achieve multiple turnover catalysis .
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The expected taxonomic range for this enzyme is: Eukaryota, Bacteria, Archaea
Reaction Schemes
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(ribonucleotide)n-2',3'-cyclophosphate
+
5'-hydroxy-(ribonucleotide)m
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=
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Synonyms
rtcb-1, rtcb1, rna-splicing ligase, more
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
(ribonucleotide)n-2',3'-cyclophosphate + 5'-hydroxy-(ribonucleotide)m + GTP + H2O = (ribonucleotide)n+m + GMP + diphosphate
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(2) overall reaction
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(ribonucleotide)n-2',3'-cyclophosphate + H2O = (ribonucleotide)n-3'-phosphate
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(2a)
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(ribonucleotide)n-3'-(5'-diphosphoguanosine) + 5'-hydroxy-(ribonucleotide)m = (ribonucleotide)n+m + GMP
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(1c); (2d)
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(ribonucleotide)n-3'-phosphate + 5'-hydroxy-(ribonucleotide)m + GTP = (ribonucleotide)n+m + GMP + diphosphate
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(1) overall reaction
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5'-guanosyl [RNA ligase]-Ntau-phosphono-L-histidine + (ribonucleotide)n-3'-phosphate = (ribonucleotide)n-3'-(5'-diphosphoguanosine) + [RNA ligase]-L-histidine
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(1b); catalytic reaction mechanism, detailed overview
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GTP + [RNA ligase]-L-histidine = 5'-guanosyl [RNA ligase]-Ntau-phosphono-L-histidine + diphosphate
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(1a); (2b)
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[RNA ligase]-Ntau-(5'-guanosyl-phosphono)-L-histidine + (ribonucleotide)n-3'-phosphate = (ribonucleotide)n-3'-(5'-diphosphoguanosine) + [RNA ligase]-L-histidine
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(2c)
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PATHWAY SOURCE
PATHWAYS
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