| 铜离子对烟草多酚氧化酶变性和复性影响的热力学研究(英) |
| Thermodynamic Studies on Cu2+-induced Unfolding and/or Refolding of COI from Tobacco |
|
| 摘要: 在有无5 mmol·L-1 CuSO4存在的两种情况下，运用荧光光谱研究了烟草多酚氧化酶在盐酸胍诱导下的变性和复性平衡。烟草多酚氧化酶在6.0 mol·L-1盐酸胍变性30 min(25 ℃)即完全失活。荧光光谱结果表明：铜离子能够提高烟草多酚氧化酶的结构稳定性和抗盐酸胍变性的能力，进而影响烟草多酚氧化酶在盐酸胍诱导下的变性和复性过程。没有外源铜存在的情况下，盐酸胍诱导的烟草多酚氧化酶变性和复性是一个可逆的二态过程；在5 mmol·L-1 CuSO4存在的条件下，由于结合了Cu2+的酶的中间态稳定性增加，显示特征荧光，结果显示，外源铜存在时，盐酸胍诱导的烟草多酚氧化酶变性和复性是一个可逆的三态过程。根据相应模型，进行了热力学计算。上述实验结果得到酶活性测定的进一步证实，在6 mol·L-1盐酸胍中放置5，10，15，20，25，30 min，烟草多酚氧化酶的剩余活性分别为18.7%，11.7%，8.9%，6.6%，3.6%，0.06%，但在5 mmol·L-1 CuSO4存在的条件下，剩余活性则分别为60.3%，44.6%，42.5%，40.2%，25.6%，25.3%。 |
| 关键词: 铜离子 多酚氧化酶 荧光光谱 变性 复性 |
| 基金项目: |
| Abstract: The equilibrium between unfolding and refolding of catechol oxidase I (COI) from tobacco in guanidine hydrochloride (GdnHCl) solutions both in the absence and in the presence of 5 mmol·L-1 CuSO4 was studied by using the fluorescence spectroscopy. Incubating COI at 6 mol·L-1 GdnHCl for 30 min (25 ℃) deactivated the enzymatic activity completely. The results obtained from the analysis of the intrinsic fluorescence of Trp residues in COI show that Cu2+ could increase the structural stability of COI against GdnHCl and, further, influence its unfolding/refolding procedure. The GdnHCl-induced unfolding/refolding of COI in the absence of 5 mmol·L-1 CuSO4 follows a two-state process with no detectable intermediate state, however, the GdnHCl-induced unfolding/refolding of COI is realized through a three-state process with an intermediate state in the presence of 5 mmol·L-1 CuSO4. In addition, the presence of Cu2+ shifts both the initial zone and the ending zone of the denaturation curve toward higher concentration. The fact that the unfolding curve and refolding curve are nearly superimposable also indicates that the unfolding/refolding is reversible both in the absence and in the presence of 5 mmol·L-1 CuSO4. |
| Keywords: tobacco catechol oxidase fluorescence unfolding refolding |
| 投稿时间：2004-10-10 修订日期：2005-01-04 |
| 摘要点击次数: 1120 |
| 全文下载次数: 1394 |
| 肖厚荣,刘清亮,徐小龙,施春华.铜离子对烟草多酚氧化酶变性和复性影响的热力学研究(英)[J].无机化学学报,2005,21(4):505-510. |
| 查看全文 查看/发表评论 下载PDF阅读器 |
| Support information: |
|
|
|
|
|
|
