Investigation of Citrullinemia Type I Variants by In Vitro Expression Studies
Investigation of Citrullinemia Type I Variants by In Vitro Expression Studies
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DOI：
10.1002/humu.20784
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发表时间：
2008-10-01
期刊：
影响因子：
3.9
通讯作者：
Haeberle, Johannes
中科院分区：
文献类型：
--
作者：
Berning, Christoph;Bieger, Iris;Haeberle, Johannes
轻度瓜氨酸血症是典型瓜氨酸血症I型的等位基因变异，也是由尿素循环酶精氨酸琥珀酸合成酶（ASS）缺乏引起的。受影响的患者包括生化但没有临床表型。然而，没有可靠的参数允许关于疾病的过程或其表现类型的结论。本研究的目的是测试不同水平的ASS残留活性对诊断时严重程度的重要性。细菌体外表达研究允许酶切分析纯化的野生型和突变型ASS蛋白p.a ala118thr （C . 352g > A）、p.p trp179arg （C . 535t > C）、p.p va1263met （C . 787g > A）、p.p arg265cys （C . 793c > T）、p.p met302val （C . 904a > G）、p.p gly324ser （C . 970g > A）、p.p gly362val （C . 1085g > T）和p.p gly390arg （C . 1168g > A）。在选择的系统中，经典突变不显示任何显著的酶活性，而与轻度病程相关的突变产生显著的ASS活性水平。突变p.a ala118thr （c.352G > A）具有高残留活性（62%），但对底物瓜氨酸和天冬氨酸的亲和力严重降低。该突变是在一名迄今为止健康的女性成人中发现的，她没有已知的瓜氨酸血症史，她在产后死于高氨血症昏迷。这项研究的结果表明，即使是高水平的残余ASS活性也不是一个稳定的临床过程的可靠预后标志。因此，测定ASS残留活性并不能帮助预测代谢紊乱的风险。这项研究应该指导临床医生以及轻度瓜氨酸血症患者终身意识到这种疾病。植物学报29(10),1222-1227,2008。(c) 2008 Wiley-Liss, Inc。
Mild citrullinemia is an allelic variant of classical citrullinemia type I also caused by deficiency of the urea cycle enzyme argininosuccinate synthetase (ASS). Affected patients comprise a biochemical but no clinical phenotype. However, there is no reliable parameter allowing conclusions regarding the course of the disorder or its type of manifestation. The aim of this study was to test the importance of varying levels of ASS residual activities for the severity at diagnosis. Bacterial in vitro expression studies allowed the enzymatic analysis of purified wild-type and the mutant ASS proteins p.Ala118Thr (c.352G > A), p.Trp179Arg (c.535T > C) p.Va1263Met (c.787G > A), p.Arg265Cys (c.793C > T), p.Met302Val (c.904A > G), P.Gly324Ser (c.970G > A), p.Gly362Val (c.1085G > T), and p.Gly390Arg (c.1168G > A). In the chosen system, classical mutations do not show any significant enzymatic activity, whereas mutations associated with a mild course yield significant ASS activity levels. The mutation p.Ala118Thr (c.352G > A) impresses by a high residual activity (62%) but a severe reduction of affinity toward the substrates citrulline and aspartate. This mutation was identified in a hitherto healthy female adult with no history of known citrullinemia who had died during the postpartum period from hyperammonemic coma. The results of this study suggest that even a high level of residual ASS activity is not a reliable prognostic marker for an uneventful clinical course. Determination of ASS residual activities, therefore, cannot help in anticipating the risk of metabolic derangement. This study should guide clinicians as well as patients with mild citrullinemia toward a lifelong awareness of the disorder. Hum Mutat 29(10), 1222-1227, 2008. (c) 2008 Wiley-Liss, Inc.