Adenine nucleoside dialdehydes: potent inhibitors of bovine liver S-adenosylhomocysteine hydrolase.
Adenine nucleoside dialdehydes: potent inhibitors of bovine liver S-adenosylhomocysteine hydrolase.
复制标题
DOI：
10.1021/bi00326a010
复制
发表时间：
1985-02
期刊：
影响因子：
2.9
通讯作者：
U. Patel-Thombre;R. Borchardt
中科院分区：
文献类型：
--
作者：
U. Patel-Thombre;R. Borchardt
各种核糖核苷 2',3'-二醛，包括腺苷二醛、S-腺苷高半胱氨酸 (AdoHcy) 二醛和 5-(甲硫基)-5'-脱氧腺苷 (MTA) 二醛，被证明是牛肝 AdoHcy 水解酶 (EC 3.3.1.1) 的有效抑制剂。这些核糖核苷 2',3'-二醛导致 AdoHcy 水解酶的时间依赖性和浓度依赖性失活。这种失活似乎是不可逆的，因为在磷酸盐缓冲液中长时间透析后酶活性无法恢复。然而，当灭活的酶在氮缓冲液[例如三（羟甲基）氨基甲烷（Tris）]中透析时，大部分酶活性可以恢复。然而，这种抑制作用的逆转可以通过在 Tris 缓冲液中透析之前用硼氢化钠预处理配体-酶复合物来防止。包含底物（例如腺苷或 AdoHcy）可以保护酶免受核糖核苷 2',3'-二醛诱导的失活。这些数据表明，酶和抑制剂之间形成的键可能是抑制剂的醛官能团和腺苷-AdoHcy结合位点中或周围的蛋白质赖氨酰残基之间的席夫碱键。当使用[2,8-3H]腺苷二醛时，测定每nmol AdoHcy水解酶结合1.73nmol抑制剂的化学计量。使用 Ackermann-Potter 方法对酶失活动力学进行的分析表明，腺苷二醛是一种紧密结合抑制剂，其化学计量为一到两个抑制剂分子与一个酶分子（四聚体）结合，Ki = 2.39 nM。
Various ribonucleoside 2',3'-dialdehydes, including adenosine dialdehyde, S-adenosylhomocysteine (AdoHcy) dialdehyde, and 5-(methylthio)-5'-deoxyadenosine (MTA) dialdehyde, were shown to be potent inhibitors of bovine liver AdoHcy hydrolase (EC 3.3.1.1). These ribonucleoside 2',3'-dialdehydes produce both time-dependent and concentration-dependent inactivation of the AdoHcy hydrolase. The inactivation appears to be irreversible since the enzyme activity cannot be recovered after prolonged dialysis against phosphate buffer. However, a substantial percentage of the enzyme activity could be recovered when the inactivated enzyme was dialyzed against a nitrogen buffer [e.g., tris(hydroxymethyl)aminomethane (Tris)]. This reversal of inhibition could be prevented, however, by pretreatment of the ligand-enzyme complex with sodium borohydride prior to dialysis in Tris buffer. Inclusion of substrates (e.g., adenosine or AdoHcy) afforded protection of the enzyme from the inactivation induced by the ribonucleoside 2',3'-dialdehydes. These data suggest that the bond formed between the enzyme and the inhibitor is probably a Schiff base linkage between the aldehydic functionality of the inhibitor and a protein lysinyl residue in or around the adenosine-AdoHcy binding site. When [2,8-3H]adenosine dialdehyde was used, a stoichiometry of 1.73 nmol of inhibitor bound per nmol of AdoHcy hydrolase was determined. Analysis of the kinetics of enzyme inactivation using the Ackermann-Potter approach indicates that adenosine dialdehyde is a tight-binding inhibitor, exhibiting a stoichiometry of one to two molecules of inhibitor bound to one molecule (tetramer) of enzyme and a Ki = 2.39 nM.