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6.5.1.8: 3'-phosphate/5'-hydroxy nucleic acid ligase

This is an abbreviated version!
For detailed information about 3'-phosphate/5'-hydroxy nucleic acid ligase, go to the full flat file.

Word Map on EC 6.5.1.8

Reaction

(ribonucleotide)n-2',3'-cyclophosphate
+
5'-hydroxy-(ribonucleotide)m
+
GTP
+
H2O
=
(ribonucleotide)n+m
+
GMP
+
diphosphate

Synonyms

3'-P RNL, MXAN_0280, MXAN_4982, RNA-splicing ligase, rtcB, RtcB RNA ligase, Rtcb-1, RtcB1, Trl1, tRNA splicing ligase, tRNA-splicing ligase

ECTree

     6 Ligases
         6.5 Forming phosphoric-ester bonds
             6.5.1 Ligases that form phosphoric-ester bonds (only sub-subclass identified to date)
                6.5.1.8 3'-phosphate/5'-hydroxy nucleic acid ligase

Systematic Name

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

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SYSTEMATIC NAME
IUBMB Comments
poly(ribonucleotide)-3'-phosphate:5'-hydroxy-poly(ribonucleotide) ligase (GMP-forming)
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 [6]. 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 [9]. The metazoan enzyme requires activating cofactors in order to achieve multiple turnover catalysis [8].