IUBMB Enzyme Nomenclature


Accepted name: protein-L-histidine (3S)-3-hydroxylase

Reaction: a [protein]-L-histidine + 2-oxoglutarate + O2 = a [protein]-(3S)-3-hydroxy-L-histidine + succinate + CO2

Other name(s): RIOX1 (gene name); RIOX2 (gene name); protein histidyl hydroxylase

Systematic name: protein-L-histidine,2-oxoglutarate:oxygen oxidoreductase (3S-hydroxylating)

Comments: The human enzymes encoded by the RIOX1 and RIOX2 genes catalyse the hydroxylation of L-histidine residues in the 60S ribosomal proteins Rpl8 and L27a, respectively. Both proteins contain JmjC and winged helix domains, and both also catalyse histone L-lysine demethylation activities.

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


1. Ge, W., Wolf, A., Feng, T., Ho, C.H., Sekirnik, R., Zayer, A., Granatino, N., Cockman, M.E., Loenarz, C., Loik, N.D., Hardy, A.P., Claridge, T.DW., Hamed, R.B., Chowdhury, R., Gong, L., Robinson, C.V., Trudgian, D.C., Jiang, M., Mackeen, M.M., Mccullagh, J.S., Gordiyenko, Y., Thalhammer, A., Yamamoto, A., Yang, M., Liu-Yi, P., Zhang, Z., Schmidt-Zachmann, M., Kessler, B.M., Ratcliffe, P.J., Preston, G.M., Coleman, M.L. and Schofield, C.J. Oxygenase-catalyzed ribosome hydroxylation occurs in prokaryotes and humans. Nat. Chem. Biol. 8 (2012) 960-962. [PMID: 23103944]

2. Bundred, J.R., Hendrix, E. and Coleman, M.L. The emerging roles of ribosomal histidyl hydroxylases in cell biology, physiology and disease. Cell. Mol. Life Sci. 75 (2018) 4093-4105. [PMID: 30151692]

[EC created 2022]

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