The Enzyme Database

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EC 4.6.1.24     
Accepted name: ribonuclease T1
Reaction: [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
Other name(s): barnase; bacterial ribonuclease Sa; guanyloribonuclease; Aspergillus oryzae ribonuclease; RNase N1; RNase N2; ribonuclease N3; ribonuclease U1; ribonuclease F1; ribonuclease Ch; ribonuclease PP1; ribonuclease SA; RNase F1; ribonuclease C2; binase; RNase Sa; guanyl-specific RNase; RNase G; RNase T1; ribonuclease guaninenucleotido-2′-transferase (cyclizing); ribonuclease N1
Systematic name: [RNA]-guanosine 5′-hydroxy-ribonucleotide-3′-[RNA fragment]-lyase (cyclicizing; [RNA fragment]-3′-guanosine-2′,3′-cyclophosphate-forming and hydrolysing)
Comments: 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.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Takahashi, K. The structure and function of ribonuclease T1. I. Chromatographic purification and properties of ribonuclease T1. J. Biochem. (Tokyo) 49 (1961) 1–8. [DOI]
2.  Kasai, K., Uchida, T., Egami, F., Yoshida, K. and Nomoto, M. Purification and crystallization of ribonuclease N1 from Neurospora crassa. J. Biochem. (Tokyo) 66 (1969) 389–396. [PMID: 5348588]
3.  Loverix, S., Laus, G., Martins, J.C., Wyns, L. and Steyaert, J. Reconsidering the energetics of ribonuclease catalysed RNA hydrolysis. Eur. J. Biochem. 257 (1998) 286–290. [PMID: 9799130]
[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]
 
 


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