Rigobello Maria Pia, Vianello Fabio, Folda Alessandra, Roman Chiara, Scutari Guido, Bindoli Alberto
Dipartimento di Chimica Biologica, Università di Padova, Viale G. Colombo 3, 35121 Padova, Italy.
Biochem Biophys Res Commun. 2006 May 12;343(3):873-8. doi: 10.1016/j.bbrc.2006.03.050. Epub 2006 Mar 20.
The effect of calcium ions has been studied on three different isoforms of thioredoxin reductase. The cytosolic (TrxR1), mitochondrial (TrxR2), and the Escherichia coli enzymes were examined and compared. In our condition, TrxR1 appears extremely sensitive to Ca2+ showing an IC50 of about 160 nM, while Ca2+ exerts only a weak inhibitory effect on the mitochondrial isoform. The thioredoxin reductase purified from E. coli is almost completely insensitive to calcium ions. Circular dichroism analysis of highly purified mitochondrial and cytosolic thioredoxin reductases reveals that Ca2+ induces conformational alterations that are particularly relevant only in the cytosolic isoform. These observations are discussed with reference to the physiological role and, in particular, to the regulatory functions of the thioredoxin system.
研究了钙离子对三种不同亚型硫氧还蛋白还原酶的影响。对胞质型（TrxR1）、线粒体型（TrxR2）以及大肠杆菌中的该酶进行了检测和比较。在我们的实验条件下，TrxR1对Ca2+表现出极高的敏感性，IC50约为160 nM，而Ca2+对线粒体亚型仅产生微弱的抑制作用。从大肠杆菌中纯化的硫氧还蛋白还原酶几乎对钙离子完全不敏感。对高度纯化的线粒体和胞质硫氧还蛋白还原酶进行的圆二色性分析表明，Ca2+诱导的构象改变仅在胞质亚型中尤为显著。结合硫氧还蛋白系统的生理作用，特别是调节功能，对这些观察结果进行了讨论。
