Wilson J M, Tarr G E, Kelley W N
Proc Natl Acad Sci U S A. 1983 Feb;80(3):870-3. doi: 10.1073/pnas.80.3.870.
We have investigated the molecular basis for a deficiency of the enzyme hypoxanthine (guanine) phosphoribosyltransferase (HPRT; IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) in a patient with a severe form of gout. We reported in previous studies the isolation of a unique structural variant of HPRT from this patient's erythrocytes and cultured lymphoblasts. This enzyme variant, which is called HPRTLondon, is characterized by a decreased concentration of HPRT protein in erythrocytes and lymphoblasts, a normal Vmax, a 5-fold increased Km for hypoxanthine, a normal isoelectric point, and an apparently smaller subunit molecular weight. Comparative peptide mapping experiments revealed a single abnormal tryptic peptide in HPRTLondon. Edman degradation of the aberrant peptide from HPRTLondon identified a serine-to-leucine amino acid substitution at position 109. This substitution can be explained by a single nucleotide change in the codon for serine-109 (UCA leads to UUA). Thus a mutation at the HPRT locus has now been defined at the molecular level.
我们研究了一名重症痛风患者体内次黄嘌呤（鸟嘌呤）磷酸核糖基转移酶（HPRT；肌苷酸：焦磷酸磷酸核糖基转移酶，EC 2.4.2.8）缺乏的分子基础。我们在之前的研究中报告了从该患者的红细胞和培养的淋巴母细胞中分离出一种独特的HPRT结构变异体。这种酶变异体被称为HPRT伦敦型，其特征是红细胞和淋巴母细胞中HPRT蛋白浓度降低、Vmax正常、次黄嘌呤的Km值增加5倍、等电点正常以及亚基分子量明显较小。比较肽图谱实验显示HPRT伦敦型中有一个异常的胰蛋白酶肽段。对HPRT伦敦型异常肽段进行的埃德曼降解确定了第109位丝氨酸到亮氨酸的氨基酸替换。这种替换可由丝氨酸109密码子中的单个核苷酸变化（UCA变为UUA）来解释。因此，现在已在分子水平上确定了HPRT基因座的突变。
