Kinetic characterization of protein arginine deiminase 4: A transcriptional corepressor implicated in the onset and progression of rheumatoid arthritis
Kinetic characterization of protein arginine deiminase 4: A transcriptional corepressor implicated in the onset and progression of rheumatoid arthritis
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DOI：
10.1021/bi050292m
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发表时间：
2005-08-09
期刊：
影响因子：
2.9
通讯作者：
Thompson, PR
中科院分区：
文献类型：
--
作者：
Kearney, PL;Bhatia, M;Thompson, PR
蛋白精氨酸脱亚胺酶4 （PAD4）是一种Ca2+依赖性酶，在许多蛋白质中催化翻译后精氨酸转化为瓜氨酸（Arg -> Cit）。虽然编码该酶的基因与类风湿性关节炎（RA）的病理生理有关，但对其催化机制、体内作用或在RA病理生理中的作用知之甚少；然而，最近的报道表明，这种酶可以作为雌激素受体的转录辅抑制因子。在此，我们报告了人类PAD4的初始动力学和机理表征。具体来说，这些研究证实了PAD4催化Arg残基水解脱亚反应生成Cit和氨。PAD4的金属依赖性也被评估，结果表明PAD4活性对钙具有高度特异性。钙活化PAD4在中高微摩尔范围内与K-0.5值表现出正的协同性。证据表明，钙结合引起构象变化也提出。此外，一些基于h4的组蛋白肽底物和苯甲酰化精氨酸衍生物的稳态动力学参数已经确定。这些化合物的k -m值在高微摩尔到低毫摩尔范围内，k（cat）值在2.8到6.6 s（-1）之间。对PAD4催化甲基化精氨酸残基去亚胺化的能力也进行了评价，结果表明这些化合物是较差的PAD4底物（V/K）
Protein arginine deiminase 4 (PAD4) is a Ca2+-dependent enzyme that catalyzes the posttranslational conversion of arginine to citrulline (Arg -> Cit) in a number of proteins, including histories. While the gene encoding this enzyme has been implicated in the pathophysiology of rheumatoid arthritis (RA), little is known about its mechanism of catalysis, its in vivo role, or its role in the pathophysiology of RA; however, recent reports suggest that this enzyme can act as a transcriptional corepressor for the estrogen receptor. Herein, we report our initial kinetic and mechanistic characterization of human PAD4. Specifically, these studies confirm that PAD4 catalyzes the hydrolytic deimination of Arg residues to produce Cit and ammonia. The metal dependence of PAD4 has also been evaluated, and the results indicate that PAD4 activity is highly specific for calcium. Calcium activation of PAD4 catalysis exhibits positive cooperativity with K-0.5 values in the mid to high micromolar range. Evidence indicating that calcium binding causes a conformational change is also presented. Additionally, the steady-state kinetic parameters for a number of histone H4-based peptide substrates and benzoylated Arg derivatives have been determined. K-m, values for these compounds are in the high micromolar to the low millimolar range with k(cat) values ranging from 2.8 to 6.6 s(-1). The ability of PAD4 to catalyze the deimination of methylated Arg residues has also been evaluated, and the results indicate that these compounds are poor PAD4 substrates (V/K