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

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

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

[RNA] containing guanosine;
H2O [CPD:C00001];
[RNA fragment]-3'-guanosine-2',3'-cyclophosphate

A family of related enzymes found in some fungi and bacteria. The enzyme is specific for cleavage at the 3'-phosphate group of guanosine in single stranded RNA, and catalyses a two-stage endonucleolytic cleavage. The first reaction produces 5'-hydroxy-phosphooligonucletides and 3'-phosphooligonucleotides ending in 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.

EC 4.6.1.24 created 1961 as EC 3.1.4.8, transferred 1965 to EC 2.7.7.26, reinstated 1972 as EC 3.1.4.8, transferred 1978 to EC 3.1.27.3, transferred 2020 to EC 4.6.1.24