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ENZYME entry: EC 4.6.1.20

Accepted Name
Ribonuclease U(2).
Alternative Name(s)
(RNA)-purine 5'-hydroxy-ribonucleotide-3'-(RNA fragment)-lyase (cyclicizing; (RNA fragment)-3'-purine-nucleoside -2',3'-cyclophosphate- forming and hydrolyzing).
Ribonuclease U2.
RNase U(2).
Reaction catalysed
  • (RNA) containing adenosine + H(2)O <=> an (RNA fragment)-3'-adenosine-3'-phosphate + a 5'-hydroxy-ribonucleotide-3'-(RNA fragment)
  • (RNA) containing guanosine + H(2)O <=> an (RNA fragment)-3'-guanosine-3'-phosphate + a 5'-hydroxy-ribonucleotide-3'-(RNA fragment)
Comment(s)
  • The enzyme secreted by the fungus Ustilago sphaerogena cleaves at the 3'-phosphate group of purines, and catalyzes a two-stage endonucleolytic cleavage.
  • The first reaction produces 5'-hydroxy-phosphooligonucletides and 3'-phosphooligonucleotides ending in Ap or Gp with 2',3'-cyclic phosphodiester, which are released from the enzyme.
  • The enzyme then hydrolyzes these cyclic compounds in a second reaction that takes place only when all the susceptible 3',5'-phosphodiester bonds have been cyclised.
  • The second reaction is a reversal of the first reaction using the hydroxyl group of water instead of the 5'-hydroxyl group of ribose.
  • The overall process is that of a phosphorus-oxygen lyase followed by hydrolysis to form the 3'-nucleotides.
  • Formerly EC 3.1.27.4.
Cross-references
BRENDA4.6.1.20
EC2PDB4.6.1.20
ExplorEnz4.6.1.20
PRIAM enzyme-specific profiles4.6.1.20
KEGG Ligand Database for Enzyme Nomenclature4.6.1.20
IUBMB Enzyme Nomenclature4.6.1.20
IntEnz4.6.1.20
MEDLINEFind literature relating to 4.6.1.20
MetaCyc4.6.1.20
UniProtKB/Swiss-Prot
P00654, RNU2_USTSP

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