IUBMB Enzyme Nomenclature


Accepted name: S-inosyl-L-homocysteine hydrolase

Reaction: S-inosyl-L-homocysteine + H2O = inosine + L-homocysteine

Other name(s): SIHH

Systematic name: S-inosyl-L-homocysteine hydrolase (inosine-forming)

Comments: The enzyme, characterized from the methanogenic archaeon Methanocaldococcus jannaschii, binds an NAD+ cofactor. It participates in an alternative pathway for the regeneration of S-adenosyl-L-methionine from S-adenosyl-L-homocysteine that involves the deamination of the latter to S-inosyl-L-homocysteine.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Miller, D., Xu, H. and White, R.H. S-Inosyl-L-homocysteine hydrolase, a novel enzyme involved in S-adenosyl-L-methionine recycling. J. Bacteriol. 197 (2015) 2284-2291. [PMID: 25917907]

[EC created 2020]

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