[HPRT_HUMAN] Defects in HPRT1 are the cause of Lesch-Nyhan syndrome (LNS) [MIM:300322]. LNS is characterized by complete lack of enzymatic activity that results in hyperuricemia, choreoathetosis, mental retardation, and compulsive self-mutilation. Defects in HPRT1 are the cause of gout HPRT-related (GOUT-HPRT) [MIM:300323]; also known as HPRT-related gout or Kelley-Seegmiller syndrome. Gout is characterized by partial enzyme activity and hyperuricemia. [:]
[HPRT_HUMAN] Converts guanine to guanosine monophosphate, and hypoxanthine to inosine monophosphate. Transfers the 5-phosphoribosyl group from 5-phosphoribosylpyrophosphate onto the purine. Plays a central role in the generation of purine nucleotides through the purine salvage pathway.
Site-directed mutagenesis was used to replace Lys68 of the human hypoxanthine phosphoribosyltransferase (HGPRTase) with alanine to exploit this less reactive form of the enzyme to gain additional insights into the structure activity relationship of HGPRTase. Although this substitution resulted in only a minimal (one- to threefold) increase in the Km values for binding pyrophosphate or phosphoribosylpyrophosphate, the catalytic efficiencies (k(cat)/Km) of the forward and reverse reactions were more severely reduced (6- to 30-fold), and the mutant enzyme showed positive cooperativity in binding of alpha-D-5-phosphoribosyl-1-pyrophosphate (PRPP) and nucleotide. The K68A form of the human HGPRTase was cocrystallized with 7-hydroxy [4,3-d] pyrazolo pyrimidine (HPP) and Mg PRPP, and the refined structure reported. The PRPP molecule built into the [(Fo - Fc)phi(calc)] electron density shows atomic interactions between the Mg PRPP and enzyme residues in the pyrophosphate binding domain as well as in a long flexible loop (residues Leu101 to Gly111) that closes over the active site. Loop closure reveals the functional roles for the conserved SY dipeptide of the loop as well as the molecular basis for one form of gouty arthritis (S103R). In addition, the closed loop conformation provides structural information relevant to the mechanism of catalysis in human HGPRTase.
Ternary complex structure of human HGPRTase, PRPP, Mg2+, and the inhibitor HPP reveals the involvement of the flexible loop in substrate binding.,Balendiran GK, Molina JA, Xu Y, Torres-Martinez J, Stevens R, Focia PJ, Eakin AE, Sacchettini JC, Craig SP 3rd Protein Sci. 1999 May;8(5):1023-31. PMID:10338013
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
↑ Wilson JM, Kelley WN. Molecular basis of hypoxanthine-guanine phosphoribosyltransferase deficiency in a patient with the Lesch-Nyhan syndrome. J Clin Invest. 1983 May;71(5):1331-5. PMID:6853716
↑ Davidson BL, Pashmforoush M, Kelley WN, Palella TD. Genetic basis of hypoxanthine guanine phosphoribosyltransferase deficiency in a patient with the Lesch-Nyhan syndrome (HPRTFlint). Gene. 1988 Mar 31;63(2):331-6. PMID:3384338
↑ Davidson BL, Palella TD, Kelley WN. Human hypoxanthine-guanine phosphoribosyltransferase: a single nucleotide substitution in cDNA clones isolated from a patient with Lesch-Nyhan syndrome (HPRTMidland). Gene. 1988 Aug 15;68(1):85-91. PMID:3265398
↑ Fujimori S, Davidson BL, Kelley WN, Palella TD. Identification of a single nucleotide change in the hypoxanthine-guanine phosphoribosyltransferase gene (HPRTYale) responsible for Lesch-Nyhan syndrome. J Clin Invest. 1989 Jan;83(1):11-3. PMID:2910902 doi:http://dx.doi.org/10.1172/JCI113846
↑ Gibbs RA, Nguyen PN, Edwards A, Civitello AB, Caskey CT. Multiplex DNA deletion detection and exon sequencing of the hypoxanthine phosphoribosyltransferase gene in Lesch-Nyhan families. Genomics. 1990 Jun;7(2):235-44. PMID:2347587
↑ Skopek TR, Recio L, Simpson D, Dallaire L, Melancon SB, Ogier H, O'Neill JP, Falta MT, Nicklas JA, Albertini RJ. Molecular analyses of a Lesch-Nyhan syndrome mutation (hprtMontreal) by use of T-lymphocyte cultures. Hum Genet. 1990 Jun;85(1):111-6. PMID:2358296
↑ Gordon RB, Sculley DG, Dawson PA, Beacham IR, Emmerson BT. Identification of a single nucleotide substitution in the coding sequence of in vitro amplified cDNA from a patient with partial HPRT deficiency (HPRTBRISBANE). J Inherit Metab Dis. 1990;13(5):692-700. PMID:2246854
↑ Tarle SA, Davidson BL, Wu VC, Zidar FJ, Seegmiller JE, Kelley WN, Palella TD. Determination of the mutations responsible for the Lesch-Nyhan syndrome in 17 subjects. Genomics. 1991 Jun;10(2):499-501. PMID:2071157
↑ Burgemeister R, Rotzer E, Gutensohn W, Gehrke M, Schiel W. Identification of a new missense mutation in exon 2 of the human hypoxanthine phosphoribosyltransferase gene (HPRTIsar): a further example of clinical heterogeneity in HPRT deficiencies. Hum Mutat. 1995;5(4):341-4. PMID:7627191 doi:http://dx.doi.org/10.1002/humu.1380050413
↑ Liu G, Aral B, Zabot MT, Kamoun P, Ceballos-Picot I. The molecular basis of hypoxanthine-guanine phosphoribosyltransferase deficiency in French families; report of two novel mutations. Hum Mutat. 1998;Suppl 1:S88-90. PMID:9452051
↑ Wilson JM, Kobayashi R, Fox IH, Kelley WN. Human hypoxanthine-guanine phosphoribosyltransferase. J Biol Chem. 1983 May 25;258(10):6458-60. PMID:6853490
↑ Wilson JM, Tarr GE, Kelley WN. Human hypoxanthine (guanine) phosphoribosyltransferase: an amino acid substitution in a mutant form of the enzyme isolated from a patient with gout. Proc Natl Acad Sci U S A. 1983 Feb;80(3):870-3. PMID:6572373
↑ Wilson JM, Kelley WN. Human hypoxanthine-guanine phosphoribosyltransferase. Structural alteration in a dysfunctional enzyme variant (HPRTMunich) isolated from a patient with gout. J Biol Chem. 1984 Jan 10;259(1):27-30. PMID:6706936
↑ Cariello NF, Scott JK, Kat AG, Thilly WG, Keohavong P. Resolution of a missense mutant in human genomic DNA by denaturing gradient gel electrophoresis and direct sequencing using in vitro DNA amplification: HPRT Munich. Am J Hum Genet. 1988 May;42(5):726-34. PMID:3358423
↑ Davidson BL, Chin SJ, Wilson JM, Kelley WN, Palella TD. Hypoxanthine-guanine phosphoribosyltransferase. Genetic evidence for identical mutations in two partially deficient subjects. J Clin Invest. 1988 Dec;82(6):2164-7. PMID:3198771 doi:http://dx.doi.org/10.1172/JCI113839
↑ Davidson BL, Pashmforoush M, Kelley WN, Palella TD. Human hypoxanthine-guanine phosphoribosyltransferase deficiency. The molecular defect in a patient with gout (HPRTAshville). J Biol Chem. 1989 Jan 5;264(1):520-5. PMID:2909537
↑ Balendiran GK, Molina JA, Xu Y, Torres-Martinez J, Stevens R, Focia PJ, Eakin AE, Sacchettini JC, Craig SP 3rd. Ternary complex structure of human HGPRTase, PRPP, Mg2+, and the inhibitor HPP reveals the involvement of the flexible loop in substrate binding. Protein Sci. 1999 May;8(5):1023-31. PMID:10338013