Ogasawara N
Institute for Developmental Research, Aichi Human Service Center.
Nihon Rinsho. 1996 Dec;54(12):3207-12.
The purine salvage enzyme hypoxanthine guanine phosphoribosyl transferase (HPRT) catalyzes the transfer of phosphoribose from PRPP to the 9-position of hypoxanthine or guanine, yielding IMP or GMP, respectively. HPRT is a 217-amino acid protein and is expressed in all tissues at low levels. High levels are present in brain, specially in the basal ganglia. HPRT is encoded by a single gene on the X chromosome (Xq26), which contains nine exons, dispersed over 40 kb of genomic DNA. mRNA is about 1.6 kb in length and contains an open reading frame of 654 nucleotides. Four autosomal pseudogenes are present within the human genome. The promoter sequences lack CAAT and TATAA elements and have an extremely CpG rich promoter. Hypomethylation of CpG clusters within the first intron and hypermethylation of sites within the 3' portion of the gene correlate with gene activity. Two DNA polymorphysms are located within the HPRT gene. One is a three-allele Bam HI restriction fragment-length polymorphysm and the other is a highly informative tetranucleotide(AGAT) tandem repeat located with intron 3.
嘌呤补救酶次黄嘌呤鸟嘌呤磷酸核糖转移酶（HPRT）催化磷酸核糖从5-磷酸核糖-1-焦磷酸（PRPP）转移至次黄嘌呤或鸟嘌呤的9位，分别生成肌苷酸（IMP）或鸟苷酸（GMP）。HPRT是一种由217个氨基酸组成的蛋白质，在所有组织中均有低水平表达。在脑中含量较高，特别是在基底神经节。HPRT由位于X染色体（Xq26）上的单个基因编码，该基因包含9个外显子，分散在40kb的基因组DNA上。mRNA长度约为1.6kb，包含一个654个核苷酸的开放阅读框。人类基因组中存在四个常染色体假基因。启动子序列缺乏CAAT和TATA元件，具有一个富含CpG的启动子。第一个内含子内CpG簇的低甲基化和基因3'部分位点的高甲基化与基因活性相关。HPRT基因内有两个DNA多态性。一个是三等位基因Bam HI限制性片段长度多态性，另一个是位于内含子3内的信息丰富的四核苷酸（AGAT）串联重复序列。
