Entry
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)
BRITE hierarchy
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
Reference
Authors
GLITZ DG, DEKKER CA.
Title
STUDIES ON A RIBONUCLEASE FROM USTILAGO SPHAEROGENA. I. PURIFICATION AND PROPERTIES OF THE ENZYME.
Journal
Reference
Authors
GLITZ DG, DEKKER CA.
Title
STUDIES ON A RIBONUCLEASE FROMUSTILAGO SPHAEROGENNA. II. SPECIFICITY OF THE ENZYME.
Journal
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
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
Sequence
Other DBs
ExplorEnz - The Enzyme Database: 4.6.1.20
ExPASy - ENZYME nomenclature database: 4.6.1.20