KEGG   ENZYME: 4.6.1.20
Entry
EC 4.6.1.20                 Enzyme                                 

Name
ribonuclease U2;
purine specific endoribonuclease;
ribonuclease U3;
RNase U3;
RNase U2;
purine-specific ribonuclease;
purine-specific RNase;
Pleospora RNase;
Trichoderma koningi RNase III;
ribonuclease (purine)
Class
Lyases;
Phosphorus-oxygen lyases;
Phosphorus-oxygen lyases (only sub-subclass identified to date)
Sysname
[RNA]-purine 5'-hydroxy-ribonucleotide-3'-[RNA fragment]-lyase (cyclicizing; [RNA fragment]-3'-purine-nucleoside -2',3'-cyclophosphate-forming and hydrolysing)
Reaction(IUBMB)
(1) [RNA] containing adenosine + H2O = an [RNA fragment]-3'-adenosine-3'-phosphate + a 5'-hydroxy-ribonucleotide-3'-[RNA fragment] (overall reaction);
(1a) [RNA] containing adenosine = an [RNA fragment]-3'-adenosine-2',3'-cyclophosphate + a 5'-hydroxy-ribonucleotide-3'-[RNA fragment];
(1b) an [RNA fragment]-3'-adenosine-2',3'-cyclophosphate + H2O = an [RNA fragment]-3'-adenosine -3'-phosphate;
(2) [RNA] containing guanosine + H2O = an [RNA fragment]-3'-guanosine-3'-phosphate + a 5'-hydroxy-ribonucleotide-3'-[RNA fragment] (overall reaction);
(2a) [RNA] containing guanosine = an [RNA fragment]-3'-guanosine-2',3'-cyclophosphate + a 5'-hydroxy-ribonucleotide-3'-[RNA fragment];
(2b) an [RNA fragment]-3'-guanosine-2',3'-cyclophosphate + H2O = an [RNA fragment]-3'- guanosine-3'-phosphate
Substrate
[RNA] containing adenosine;
H2O [CPD:C00001];
[RNA fragment]-3'-adenosine-2',3'-cyclophosphate;
[RNA] containing guanosine;
[RNA fragment]-3'-guanosine-2',3'-cyclophosphate
Product
[RNA fragment]-3'-adenosine-3'-phosphate;
5'-hydroxy-ribonucleotide-3'-[RNA fragment];
[RNA fragment]-3'-adenosine-2',3'-cyclophosphate;
[RNA fragment]-3'-adenosine -3'-phosphate;
[RNA fragment]-3'-guanosine-3'-phosphate;
[RNA fragment]-3'-guanosine-2',3'-cyclophosphate;
[RNA fragment]-3'- guanosine-3'-phosphate
Comment
The enzyme secreted by the fungus Ustilago sphaerogena cleaves at the 3'-phosphate group of purines, and catalyses 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 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 4.6.1.20 created 1978 as 3.1.27.4, modified 1981, transferred 2018 to EC 4.6.1.20
Orthology
K23175  ribonuclease U2
Reference
1  [PMID:14230791]
  Authors
GLITZ DG, DEKKER CA.
  Title
STUDIES ON A RIBONUCLEASE FROM USTILAGO SPHAEROGENA. I. PURIFICATION AND PROPERTIES OF THE ENZYME.
  Journal
Biochemistry 3:1391-9 (1964)
DOI:10.1021/bi00898a001
Reference
2  [PMID:14230792]
  Authors
GLITZ DG, DEKKER CA.
  Title
STUDIES ON A RIBONUCLEASE FROMUSTILAGO SPHAEROGENNA. II. SPECIFICITY OF THE ENZYME.
  Journal
Biochemistry 3:1399-406 (1964)
DOI:10.1021/bi00898a002
Reference
3
  Authors
Uchida, T. and Egami, F. Microbial ribonucleases with special reference to RNases T1, T 2, N
  Title
1, and U2.
  Journal
In: Boyer, P.D. (Ed.), The Enzymes, 3rd ed., vol. 4, Academic Press, New York, 1971, p. 205-250.
Reference
4  [PMID:10930732]
  Authors
Martinez-Ruiz A, Garcia-Ortega L, Kao R, Onaderra M, Mancheno JM, Davies J, Martinez del Pozo A, Gavilanes JG
  Title
Ribonuclease U2: cloning, production in Pichia pastoris and affinity chromatography purification of the active recombinant protein.
  Journal
FEMS Microbiol Lett 189:165-9 (2000)
DOI:10.1111/j.1574-6968.2000.tb09224.x
  Sequence
Other DBs
ExplorEnz - The Enzyme Database: 4.6.1.20
IUBMB Enzyme Nomenclature: 4.6.1.20
ExPASy - ENZYME nomenclature database: 4.6.1.20
BRENDA, the Enzyme Database: 4.6.1.20
CAS: 37205-57-5
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