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Histidine Triad (HIT) Superfamily

  1. Charles Brenner

Published Online: 15 AUG 2014

DOI: 10.1002/9780470015902.a0020545.pub2



How to Cite

Brenner, C. 2014. Histidine Triad (HIT) Superfamily. eLS. .

Author Information

  1. University of Iowa, Iowa City, Iowa, USA

Publication History

  1. Published Online: 15 AUG 2014


Histidine triad (HIT) enzymes are an ancient superfamily of nucleotide hydrolases and transferases that catalyse mechanistically similar but biologically distinct reactions on nucleotide-containing substrates in pathways important for cellular growth, apoptosis, deoxyribonucleic acid, ribonucleic acid, vitamin and carbohydrate metabolism. Four branches of HIT enzymes function as nucleotide hydrolases. These enzymes include homologues and paralogues of histidine triad nucleotide-binding protein, fragile histidine triad protein, APRATAXIN and scavenger decapping protein, which act in various cellular compartments. One diverse branch of the HIT superfamily contains nucleotide transferases and phosphorylases related to galactose-1-phosphate uridylyltransferase, AppppA phosphorylase, adenylylsulfate: phosphate adenylyltransferase, adenosine diphosphate-glucose phosphorylase and VTC2, the guanosine diphosphate-l-galactose phosphorylase. This review provides tools to discern the identities and the probable functions of HIT enzymes from their sequences.

Key Concepts:

  • Histidine triad enzymes act on substrates containing a nucleoside monophosphate linked to distinct leaving groups.

  • HINT, FHIT, APRATAXIN and DCPS are HIT hydrolases.

  • GALT and VTC2 are HIT transferases.

  • Particular HIT enzymes are targeted to different cellular compartments to carry out their functions.

  • HIT enzymes remove nucleotide adducts from proteins and DNA and transform low-molecular-weight metabolites in cells.


  • HINT;
  • FHIT;
  • GALT;
  • VTC2;
  • DCPS