Cloning, expression, and characterization of a human inosine triphosphate pyrophosphatase encoded by the ITPA gene
Cloning, expression, and characterization of a human inosine triphosphate pyrophosphatase encoded by the ITPA gene
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DOI：
10.1074/jbc.m011084200
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发表时间：
2001-06-01
影响因子：
4.8
通讯作者：
Mao, YM
中科院分区：
文献类型：
--
作者：
Lin, SR;McLennan, AG;Mao, YM
ITP和dITP存在于所有细胞中。dITP具有潜在的致突变性，这些核苷酸的水平受肌苷三磷酸焦磷酸酶（EC 3，6，1，19）的控制。本文报道了21，5-kDa人肌苷三磷酸焦磷酸酶（hITP 3）的克隆、表达和鉴定，该酶在许多动物组织中的活性已被报道，并在群体中进行了研究，但其蛋白质序列尚未确定。在最适pH 10.0下，重组hITlatin将ITP、dITP和黄嘌呤核苷5 '-三磷酸水解为它们各自的单磷酸，而与其他核苷三磷酸的活性较低。ITP、dITP和5 '-三磷酸黄嘌呤核苷的Km值分别为0.51、0.31和0.57 mM，k（cat）值分别为580、360和640 s（-1）。活性绝对需要二价阳离子。编码hITPA cDNA序列的基因通过辐射杂交定位于染色体20 p的D20 S113-D20 S97区间，该区间与ITPA肌苷三磷酸酶基因先前定位的区间相同。BLAST搜索显示，从细菌到哺乳动物的生物体中存在许多相似的序列。这种普遍存在的蛋白质家族的功能被认为是从细胞中消除轻微的潜在致突变或致染色体断裂的嘌呤核苷三磷酸。
ITP and dITP exist in all cells. dITP is potentially mutagenic, and the levels of these nucleotides are controlled by inosine triphosphate pyrophosphatase (EC 3,6,1,19), Here we report the cloning, expression, and characterization of a 21,5-kDa human inosine triphosphate pyrophosphatase (hITPase), an enzyme whose activity has been reported in many animal tissues and studied in populations but whose protein sequence has not been determined before. At the optimal pH of 10.0, recombinant hITPase hydrolyzed ITP, dITP, and xanthosine 5'-triphosphate to their respective monophosphates whereas activity with other nucleoside triphosphates was low. K-m values for ITP, dITP, and xanthosine 5'-triphosphate were 0,51, 0,31, and 0.57 mM, respectively, and k(cat) values were 580, 360, and 640 s(-1) respectively. A divalent cation was absolutely required for activity. The gene encoding the hITPase cDNA sequence was localized by radiation hybrid mapping to chromosome 20p in the interval D20S113-D20S97, the same interval in which the ITPA inosine triphosphatase gene was previously localized. A BLAST search revealed the existence of many similar sequences in organisms ranging from bacteria to mammals. The function of this ubiquitous protein family is proposed to be the elimination of minor potentially mutagenic or clastogenic purine nucleoside triphosphates from the cell.