Histidine Triad (HIT) Superfamily
Published Online: 28 SEP 2007
Copyright © 2001 John Wiley & Sons, Ltd. All rights reserved.
How to Cite
Brenner, C. 2007. Histidine Triad (HIT) Superfamily. eLS.
- Published Online: 28 SEP 2007
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 and deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and carbohydrate metabolism. Four branches of HIT enzymes function as nucleotide hydrolases. These enzymes include homologues and paralogues of histidine triad nucleotide-binding (Hint) protein, fragile histidine triad (Fhit) protein, Aprataxin and scavenger decapping protein (Dcps). One diverse branch of the HIT superfamily contains nucleotide transferases and phosphorylases related to galactose-1-phosphate uridylyltransferase (GalT), AppppA phosphorylase, adenylylsulfate:phosphate adenylyltransferase (APAT), adenosine diphosphate (ADP)-glucose phosphorylase, and Vtc2, the guanosine diphosphate (GDP)-l-galactose phosphorylase. This review provides tools to discern the identities and the probable functions of new HIT enzymes from their sequences.