Kamatani N
Institute of Rheumatology, Tokyo Women's Medical College.
Nihon Rinsho. 1996 Dec;54(12):3213-9.
Adenine phosphoribosyltransferase (APRT) is a purine metabolic enzyme that salvages adenine moiety generated via the polyamine synthetic pathway. Adenine is produced by the cleavage of methylthiodenosine (MTA), a by-product of the polyamine synthesis. None of the normal somatic cells but about 23% of human malignant cells lack the enzyme MTA phosphorylase because of the homozygous deletion of 9p21 and are deficient in the salvage route of the adenine molecule. APRT gene is located at 16q24, is about 2200 bp long and is composed of 5 exons. The cDNA codes for 180 amino acids which include a PRPP binding domain. The Met at the N-terminal is removed and the Ala is next acetylated. The protein is cleaved into two peptides at amino acid 136 (Met) by BrCN treatment and the N-terminal peptide includes the PRPP binding domain. Although most of the somatic cells express APRT gene, some cells do not, even in normal subjects. This is because of somatic mutations. APRT locus is one of a few genetic loci where human somatic mutations can be observed. We can observe loss of heterozygosity (LOH) and point mutational events at the somatic cell level at this locus. The mode of the somatic mutations is quite similar to that observed in neoplastic cells at the tumor-suppressor loci.
腺嘌呤磷酸核糖转移酶（APRT）是一种嘌呤代谢酶，可挽救通过多胺合成途径产生的腺嘌呤部分。腺嘌呤由多胺合成的副产物甲基硫代腺苷（MTA）裂解产生。除了约23%的人类恶性细胞外，正常体细胞均不缺乏MTA磷酸化酶，因为9p21存在纯合缺失，且腺嘌呤分子的补救途径存在缺陷。APRT基因位于16q24，长约2200 bp，由5个外显子组成。cDNA编码180个氨基酸，其中包括一个PRPP结合结构域。N端的甲硫氨酸被去除，接着丙氨酸被乙酰化。用溴化氰处理后，该蛋白在氨基酸136（甲硫氨酸）处被切割成两个肽段，N端肽段包含PRPP结合结构域。尽管大多数体细胞表达APRT基因，但即使在正常受试者中，一些细胞也不表达。这是由于体细胞突变。APRT基因座是少数几个可观察到人类体细胞突变的基因座之一。在该基因座的体细胞水平上，我们可以观察到杂合性缺失（LOH）和点突变事件。体细胞突变的模式与在肿瘤抑制基因座的肿瘤细胞中观察到的模式非常相似。
