Lyases;
Phosphorus-oxygen lyases;
Phosphorus-oxygen lyases (only sub-subclass identified to date)
BRITE hierarchy

[RNA] 5'-hydroxy-ribonucleotide-3'-[RNA fragment]-lyase (cyclicizing; [RNA fragment]-3'- nucleoside-2',3'-cyclophosphate-forming and hydrolysing)

RNA + H2O = an [RNA fragment]-3'-nucleoside-3'-phosphate + a 5'-hydroxy-ribonucleotide-3'-[RNA fragment] (overall reaction);
(1a) RNA = an [RNA fragment]-3'-nucleoside-2',3'-cyclophosphate + a 5'-hydroxy-ribonucleotide-3'-[RNA fragment];
(1b) an [RNA fragment]-3'-nucleoside-2',3'-cyclophosphate + H2O = an [RNA fragment]-3'-nucleoside-3'-phosphate

RNA [CPD:C00046];
H2O [CPD:C00001];
[RNA fragment]-3'-nucleoside-2',3'-cyclophosphate

A widely distributed family of related enzymes found in protozoans, plants, bacteria, animals and viruses that cleave ssRNA 3'-phosphate group with little base specificity. The enzyme catalyses a two-stage endonucleolytic cleavage. The first reaction produces 5'-hydroxy-phosphooligonucletides and 3'-phosphooligonucleotides ending with a 2',3'-cyclic phosphodiester, which are released from the enzyme. The enzyme then hydrolyses the cyclic products 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.

EC 4.6.1.19 created 1972 as EC 3.1.4.23, transferred 1978 to EC 3.1.27.1, modified 1981, transferred 2018 to EC 4.6.1.19