Molecular Dynamics for Thermal Unfolding Behaviors of N-Carbamyl-D-Amino Acid Amidohydrolase

以分子動態模擬研究N-Carbamyl-D-Amino Acid Amidohydrolase受熱反摺疊行為

劉宣良(Hsuan-Liang Liu) ； 謝偉強(Wei-Chan Hsieh)

《Journal of the Chinese Institute of Chemical Engineers》 36卷2期 (2005/03) Pp. 185-194

https://doi.org/10.6967/JCICE.200503.0185

摘要

本研究以1 ns之分子動態模擬及溫度躍升技術研究N-Carbamyl-D-Amino Acid Amidohydrolase(CAA)雙體的受熱反摺疊行爲。CAA受熱反摺疊並非一對稱的模式，而是此二個單體分別依照不同的路徑瓦解。單體A從5最外面的第一層失去基二級結構的完整性，而單體B卻由內部的第三層最先瓦解。因此，單體B中的活性中心也比單體A中的活性中心較不穩定。此二單體中間的介面疏水區也受熱膨脹，代表CCA雙體容易受熱分解成爲不具酵素活性的單體形式，因此，本研究結果建議在此疏水區中以基因工程的方法建構一些雙硫鍵，如L218C，A222C，I301C，及A302C，用以“鎖住”這二個單體，以維持其具有活性的雙體型態，而此基因工程的研究也正在本實驗室中進行。

並列摘要

The thermal unfolding behaviors of the dimeric N-carbamyl-D-amino acid amidohydrolase (CAA) were investigated by 1 ns molecular dynamics simulations in explicit water system with temperature jump technique. Rather than a symmetrical event, the unfolding of the two subunits of the dimeric CAA follows different pathways. Although these two subunits are structurally identical, subunit A loses its secondary structure integrity from the outermost layer 1 to the innermost layer 4; whereas subunit B unfolds first from its interior layer 3, where the active site pocket is located. Hence, the active site from subunit B is less stable than that from subunit A. Furthermore, the interfacial hydrophobic region is expanded, implying that the dimeric CAA tends to dissociate into the enzymatically inactive monomeric form. It further indicates that the interior layers lose their secondary structure integrity, resulting in the destruction of the active site geometry. Thus, it is suggested to engineer several disulfide bonds to “bind” the interfacial hydrophobic region, such as L218C, A 222C, I301C, and A302C, which is currently being conducted in our group.

並列關鍵字

N-carbamyl-D-amino acid amidohydrolase (CAA) ； Molecular dynamics simulations ； Temperature jump technique ； Active site ； Hydrophobic ； Disulfide bond