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ENZYME entry: EC

Accepted Name
Bacteriophage T(4) restriction endoribonuclease RegB.
Reaction catalysed
A (pre-mRNA)-containing guanosine-adenosine + H(2)O <=> a 5' hydroxy-guanosine-(pre-mRNA fragment) + a (pre-mRNA fragment)-3'-adenosine-3'-phosphate
  • The enzyme from bacteriophage T(4) cleaves early mRNAs between Ap and Gp at one specific specific GpGpApGp site, favoring their further transition to middle-phase mRNA.
  • The activity is enhanced by Ribosomal S1 protein.
  • The enzyme catalyzes a two-stage endonucleolytic cleavage.
  • The first reaction produces 5'-hydroxy-phosphooligonucletides and 3'-phosphooligonucleotides ending 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.
PRIAM enzyme-specific profiles4.6.1.25
KEGG Ligand Database for Enzyme Nomenclature4.6.1.25
IUBMB Enzyme Nomenclature4.6.1.25
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