Reaction participants Show >> << Hide
- Name help_outline XMP Identifier CHEBI:57464 (Beilstein: 11352170) help_outline Charge -2 Formula C10H11N4O9P InChIKeyhelp_outline DCTLYFZHFGENCW-UUOKFMHZSA-L SMILEShelp_outline O[C@@H]1[C@@H](COP([O-])([O-])=O)O[C@H]([C@@H]1O)n1cnc2c1[nH]c(=O)[nH]c2=O 2D coordinates Mol file for the small molecule Search links Involved in 7 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline diphosphate Identifier CHEBI:33019 (Beilstein: 185088) help_outline Charge -3 Formula HO7P2 InChIKeyhelp_outline XPPKVPWEQAFLFU-UHFFFAOYSA-K SMILEShelp_outline OP([O-])(=O)OP([O-])([O-])=O 2D coordinates Mol file for the small molecule Search links Involved in 1,139 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline xanthine Identifier CHEBI:17712 (CAS: 69-89-6) help_outline Charge 0 Formula C5H4N4O2 InChIKeyhelp_outline LRFVTYWOQMYALW-UHFFFAOYSA-N SMILEShelp_outline O=c1[nH]c2[nH]cnc2c(=O)[nH]1 2D coordinates Mol file for the small molecule Search links Involved in 18 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline 5-phospho-α-D-ribose 1-diphosphate Identifier CHEBI:58017 Charge -5 Formula C5H8O14P3 InChIKeyhelp_outline PQGCEDQWHSBAJP-TXICZTDVSA-I SMILEShelp_outline O[C@H]1[C@@H](O)[C@H](O[C@@H]1COP([O-])([O-])=O)OP([O-])(=O)OP([O-])([O-])=O 2D coordinates Mol file for the small molecule Search links Involved in 22 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
RHEA:10800 | RHEA:10801 | RHEA:10802 | RHEA:10803 | |
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Reaction direction help_outline | undefined | left-to-right | right-to-left | bidirectional |
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Publications
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Crystal structure of Toxoplasma gondii hypoxanthine-guanine phosphoribosyltransferase with bound XMP, pyrophosphate and two Mg2+ ions: insights into the catalytic mechanism.
Heroux A., White E.L., Ross L.J., Davis R.L., Borhani D.W.
The crystal structure of the Toxoplasma gondii hypoxanthine-guanine phosphoribosyltransferase (HGPRT)-xanthosine 5'-monophosphate (XMP)-pyrophosphate-Mg(2+) ternary complex has been determined at 1. 60 A resolution. This biproduct, post-transition state structure is of a T. gondii HGPRT mutant (As ... >> More
The crystal structure of the Toxoplasma gondii hypoxanthine-guanine phosphoribosyltransferase (HGPRT)-xanthosine 5'-monophosphate (XMP)-pyrophosphate-Mg(2+) ternary complex has been determined at 1. 60 A resolution. This biproduct, post-transition state structure is of a T. gondii HGPRT mutant (Asp150Ala or D150A). The D150A mutant has reduced activity (k(cat) lower by 11-, 296-, and 8.6-fold for hypoxanthine, guanine, and xanthine, respectively) compared to wild-type T. gondii HGPRT. The Michaelis constants for purine bases are altered only slightly, whereas those for alpha-D-5-phosphoribosyl 1-pyrophosphate (PRPP) are lower by approximately 6.5-fold. The ternary complex crystallizes in space group C222(1) (a = 55.21 A, b = 112.25 A, and c = 144.28 A) with two subunits in the asymmetric unit; the HGPRT tetramer is completed by the application of 2-fold crystallographic symmetry. All active sites contain XMP ¿bound in a fashion similar to that of the guanosine 5'-monophosphate (GMP) and inosine 5'-monophosphate (IMP) complexes reported in the preceding article [Héroux, A., et al. (1999) Biochemistry 38, 14485-14494]¿, pyrophosphate, and two Mg(2+) ions. Each Mg(2+) ion is octahedrally coordinated by two terminal pyrophosphate oxygen atoms and several ordered water molecules. This structure shows how HGPRT uses two Mg(2+) ions to orient and activate the pyrophosphate moiety of PRPP for attack by a purine base, and why mutation in humans of the residue corresponding to Asp206, the only HGPRT amino acid that directly contacts the Mg(2+) ions, causes Lesch-Nyhan syndrome (HGPRT(Kinston), D193N). The Leu78-Lys79 peptide bond in the active site adopts the cis configuration, which it must to bind PRPP or pyrophosphate. The contribution of cis-trans isomerization of this peptide bond to the energetics of substrate binding and product release is discussed. A comprehensive description of the HGPRT reaction mechanism is also proposed. << Less