FEATURES

FAMILY

purine/pyrimidine phosphoribosyltransferase family

DESCRIPTION

Also known as HGPRT_MYCTU, hpt, hprT. Purine salvage pathway enzyme that catalyzes the transfer of the ribosyl-5-phosphate group from 5-phospho-alpha-D-ribose 1-diphosphate (PRPP) to the N9 position of the 6-oxopurines hypoxanthine and guanine to form the corresponding ribonucleotides IMP (inosine 5'-monophosphate) and GMP (guanosine 5'-monophosphate), with the release of PPi (PubMed:19362594, PubMed:25915781). Thus, specifically recycles hypoxanthine and guanine imported from the external medium, and converts them to IMP and GMP, respectively. Cannot use xanthine as substrate (PubMed:19362594). Homodimer and homotetramer in equilibrium. The presence or absence of divalent metal ions, as well as phosphate, can affect the oligomerization state of the enzyme. Likely functions as a tetramer (rather than a dimer) in its biological environment, which is the most active form. The dimeric structure is also active though ~50% of that of the tetramer.

EXTERNAL LINKS

hpt

Hypoxanthine-guanine phosphoribosyltransferase

hpt

Molecular Synopsis