KEGG   ENZYME: 4.6.1.23
Entry
EC 4.6.1.23                 Enzyme                                 

Name
ribotoxin;
alpha-sarcin;
rRNA endonuclease (ambiguous)
Class
Lyases;
Phosphorus-oxygen lyases;
Phosphorus-oxygen lyases (only sub-subclass identified to date)
Sysname
[28S-rRNA]-guanosine-adenosine 5'-hydroxy-guanosine-ribonucleotide-3'-[RNA fragment]-lyase (cyclicizing; [RNA fragment]-3'-adenosine-2',3'-cyclophosphate-forming and hydrolysing)
Reaction(IUBMB)
a 28S rRNA containing guanosine-adenosine pair + H2O = an [RNA fragment]-3'-adenosine-3'-phosphate + a 5'-a hydroxy-guanosine-3'-[RNA fragment] (overall reaction);
(1a) a 28S rRNA containing guanosine-adenosine pair = an [RNA fragment]-3'-adenosine-2',3'-cyclophosphate + a 5'-hydroxy-guanosine-3'-[RNA fragment];
(1b) an [RNA fragment]-3'-adenosine-2',3'-cyclophosphate + H2O = an [RNA fragment]-3'-adenosine-3'-phosphate
Substrate
28S rRNA containing guanosine-adenosine pair;
H2O [CPD:C00001];
[RNA fragment]-3'-adenosine-2',3'-cyclophosphate
Product
[RNA fragment]-3'-adenosine-3'-phosphate;
5'-a hydroxy-guanosine-3'-[RNA fragment];
[RNA fragment]-3'-adenosine-2',3'-cyclophosphate;
5'-hydroxy-guanosine-3'-[RNA fragment]
Comment
Ribotoxins are rRNA endonucleases that catalyse the cleavage of the phosphodiester bond between guanosine and adenosine residues at one specific position in 28S rRNA. The enzyme secreted by Aspergillus giganteus specifically cleaves rat 28S rRNA between G4325 and A4326 and displays cytotoxic activity toward animal cells. It can also act on bacterial rRNAs. The enzyme catalyses 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 hydrolyses 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.
History
EC 4.6.1.23 created 1992 as EC 3.1.27.10, transferred 2019 to EC 4.6.1.23
Orthology
K01171  rRNA endonuclease
Genes
AFM: AFUA_5G02330
ACT: ACLA_002920
NFI: NFIA_039760
TRG: TRUGW13939_02438
Reference
1  [PMID:6355092]
  Authors
Chan YL, Endo Y, Wool IG
  Title
The sequence of the nucleotides at the alpha-sarcin cleavage site in rat 28 S ribosomal ribonucleic acid.
  Journal
J Biol Chem 258:12768-70 (1983)
Reference
2  [PMID:9580156]
  Authors
Lacadena J, Martinez del Pozo A, Lacadena V, Martinez-Ruiz A, Mancheno JM, Onaderra M, Gavilanes JG
  Title
The cytotoxin alpha-sarcin behaves as a cyclizing ribonuclease.
  Journal
FEBS Lett 424:46-8 (1998)
DOI:10.1016/s0014-5793(98)00137-9
Reference
3  [PMID:29952541]
  Authors
Citores L, Iglesias R, Ragucci S, Di Maro A, Ferreras JM
  Title
Antifungal Activity of alpha-Sarcin against Penicillium digitatum: Proposal of a  New Role for Fungal Ribotoxins.
  Journal
ACS Chem Biol 13:1978-1982 (2018)
DOI:10.1021/acschembio.8b00410
Other DBs
ExplorEnz - The Enzyme Database: 4.6.1.23
IUBMB Enzyme Nomenclature: 4.6.1.23
ExPASy - ENZYME nomenclature database: 4.6.1.23
BRENDA, the Enzyme Database: 4.6.1.23
CAS: 1407-48-3
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