IUBMB Enzyme Nomenclature


Accepted name: guanosine-5'-diphospho-5'-[DNA] diphosphatase

Reaction: guanosine-5'-diphospho-5'-[DNA] + H2O = phospho-5'-[DNA] + GMP

Other name(s): aprataxin; pp5'G5'DNA diphosphatase; pp5'G5'-DNA guanylate hydrolase; APTX (gene name); HNT3 (gene name)

Systematic name: guanosine-5'-diphospho-5'-[DNA] hydrolase (guanosine 5'-phosphate-forming)

Comments: Aprataxin is a DNA-binding protein that catalyses (among other activities) the 5' decapping of Gpp-DNA (formed by homologs of RtcB3 from the bacterium Myxococcus xanthus). The enzyme binds the guanylate group to a histidine residue at its active site, forming a covalent enzyme-nucleotide phosphate intermediate, followed by the hydrolysis of the guanylate from the nucleic acid and eventual release. The enzyme forms a 5'-phospho terminus that can be efficiently joined by "classical" ligases. The enzyme also possesses the activitiy of EC, adenosine-5'-diphospho-5'-[DNA] diphosphatase and EC, DNA-3'-diphospho-5'-guanosine diphosphatase.

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


1. Maughan, W.P. and Shuman, S. Characterization of 3'-phosphate RNA ligase paralogs RtcB1, RtcB2, and RtcB3 from Myxococcus xanthus highlights DNA and RNA 5'-phosphate capping activity of RtcB3. J. Bacteriol. 197 (2015) 3616-3624. [PMID: 26350128]

[EC created 2017 as EC, transferred 2019 to EC]

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