IUBMB Enzyme Nomenclature


Accepted name: adenosylhomocysteine nucleosidase

Reaction: (1) S-adenosyl-L-homocysteine + H2O = S-(5-deoxy-D-ribos-5-yl)-L-homocysteine + adenine
(2) 5'-deoxyadenosine + H2O = 5-deoxy-D-ribose + adenine
(3) S-methyl-5'-thioadenosine + H2O = 5-(methylsulfanyl)-D-ribose + adenine

For diagram of autoinducer AI-2 biosynthesis, click here and for diagram of the methionine-salvage pathway, click here

Other name(s): S-adenosylhomocysteine hydrolase (ambiguous); S-adenosylhomocysteine nucleosidase; 5'-methyladenosine nucleosidase; S-adenosylhomocysteine/5'-methylthioadenosine nucleosidase; AdoHcy/MTA nucleosidase; MTN2 (gene name); mtnN (gene name)

Systematic name: S-adenosyl-L-homocysteine homocysteinylribohydrolase

Comments: This enzyme, found in bacteria and plants, acts on three different substrates. It is involved in the S-adenosyl-L-methionine (SAM, AdoMet) cycle, which recycles S-adenosyl-L-homocysteine back to SAM, and in salvage pathways for 5'-deoxyadenosine and S-methyl-5'-thioadenosine, which are produced from SAM during the action of many enzymes. cf. the plant enzyme EC, methylthioadenosine nucleosidase.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9055-10-1


1. Duerre, J.A. A hydrolytic nucleosidase acting on S-adenosylhomocysteine and on 5-methylthioadenosine. J. Biol. Chem. 237 (1962) 3737-3741.

2. Ferro, A.J., Barrett, A. and Shapiro, S.K. Kinetic properties and the effect of substrate analogues on 5'-methylthioadenosine nucleosidase from Escherichia coli. Biochim. Biophys. Acta 438 (1976) 487-494. [PMID: 782530]

3. Cornell, K.A., Swarts, W.E., Barry, R.D. and Riscoe, M.K. Characterization of recombinant Eschericha coli 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidase: analysis of enzymatic activity and substrate specificity. Biochem. Biophys. Res. Commun. 228 (1996) 724-732. [PMID: 8941345]

4. Park, E.Y., Choi, W.S., Oh, S.I., Kim, K.N., Shin, J.S. and Song, H.K. Biochemical and structural characterization of 5'-methylthioadenosine nucleosidases from Arabidopsis thaliana. Biochem. Biophys. Res. Commun. 381 (2009) 619-624. [PMID: 19249293]

5. Farrar, C.E., Siu, K.K., Howell, P.L. and Jarrett, J.T. Biotin synthase exhibits burst kinetics and multiple turnovers in the absence of inhibition by products and product-related biomolecules. Biochemistry 49 (2010) 9985-9996. [PMID: 20961145]

6. North, J.A., Wildenthal, J.A., Erb, T.J., Evans, B.S., Byerly, K.M., Gerlt, J.A. and Tabita, F.R. A bifunctional salvage pathway for two distinct S-adenosylmethionine by-products that is widespread in bacteria, including pathogenic Escherichia coli. Mol. Microbiol. (2020) . [PMID: 31950558]

[EC created 1972, modified 2004, modified 2020]

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