Fhit, a putative tumor suppressor in humans, is a dinucleoside 5',5'''-P-1,P-3-triphosphate hydrolase
Fhit, a putative tumor suppressor in humans, is a dinucleoside 5',5'''-P-1,P-3-triphosphate hydrolase
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DOI：
10.1021/bi961415t
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发表时间：
1996-09-10
期刊：
影响因子：
2.9
通讯作者：
Huebner, F
中科院分区：
文献类型：
--
作者：
Barnes, LD;Garrison, PN;Huebner, F
人类Fhit（脆性组氨酸三联体）蛋白由FHIT推定的肿瘤抑制基因编码，是一种典型的二核苷5 '，5三引物-P-1，P-3-三磷酸（Ap（3）A）水解酶（EC 3.6.1.29）基于其酶性质，我们在这里报告。在Ap（n）A（n = 3-6）中，Ap（3）A是较好的底物，AMP总是反应产物之一。以Ap（3）A为底物，Mn ~（2+）和Mg ~（2+）对Ap（3）A具有同样的刺激作用，而Zn ~（2+）则具有抑制作用。Ap（3）A和Ap（4）A的Km值分别为1.3和4.6 μ M。对于谷胱甘肽S-转移酶（GST）-Fhit融合蛋白，Ap（3）A和Ap（4）A的特异性常数k（cat）/K-m值分别为2.0 x 10（6）和6.7 x 10（3）s（-1）M（-1）。FHIT的定点突变表明，所有四个保守的组氨酸都是完整活性所必需的，并且三联体的中心组氨酸对于Ap（3）A水解酶活性是绝对必需的。这种假定的肿瘤抑制因子是二核苷酸寡磷酸代谢和肿瘤发生之间联系的第一个证据。此外，Fhit是第一个HIT蛋白，其中组氨酸残基已通过诱变证明对功能至关重要。
Human Fhit (fragile histidine triad) protein, encoded by the FHIT putative tumor suppressor gene, is a typical dinucleoside 5',5 triple prime-P-1,P-3-triphosphate (Ap(3)A) hydrolase (EC 3.6.1.29) on the basis of its enzymatic properties we report here. Ap(3)A is the preferred substrate among Ap(n)A (n = 3-6), and AMP is always one of the reaction products. Mn2+ and Mg2+ are equally stimulatory, while Zn2+ is inhibitory with Ap(3)A as the substrate. Values of the K-m for Ap(3)A and Ap(4)A are 1.3 and 4.6 mu M, respectively. Values of the specificity constant, k(cat)/K-m, for Ap(3)A and Ap(4)A are 2.0 x 10(6) and 6.7 x 10(3) s(-1) M(-1), respectively, for a glutathione S-transferase (GST)-Fhit fusion protein. Site-directed mutagenesis of FHIT demonstrated that all four conserved histidines are required for full activity, and the central histidine of the triad is absolutely essential for Ap(3)A hydrolase activity. This putative tumor suppressor is the first evidence for a connection between dinucleotide oligophosphate metabolism and tumorigenesis. Also, Fhit is the first HIT protein in which the histidine residues have been demonstrated by mutagenesis to be critical for function.