Ballistreri F P, Barbuzzi E G, Tomaselli G A, Toscano R M
Dipartimento di Scienze Chimiche, Università di Catania, Italy.
J Inorg Biochem. 2000 May 30;80(1-2):173-6. doi: 10.1016/s0162-0134(00)00027-1.
Kinetics of the oxidation of cysteine to cystine by four V(V) oxo diperoxo complexes [VO(O2)2L] possessing insulin mimetic activity, where L = oxalate(oxa), picolinate (pic), bipyridil (bipy), phenanthroline(phen), were performed in water at 10 degrees C by the UV or stopped-flow technique. 51V NMR spectra indicate that oxa undergoes a total ligand dissociation differently from pic, bipy and phen which hold their ligands also in solution. The observed reactivity is deeply affected by the identity of the ligand. The process seems to require coordination of the cysteine to the metal, followed by oxidation within the coordination sphere. In this respect phen and bipy make the coordination of cysteine much easier than oxa and pic. It is suggested, also on the basis of some preliminary observations concerning the oxidation of C6H5CH2SH, that the oxidation process is triggered by an electron transfer step. The rate of this step would be higher for oxa and pic than for phen and bipy. The observation that the oxidative ability of these vanadium peroxo complexes is dependent upon the nature of the ligands might match the analogous finding that their insulin mimetic activity is also modulated by the ligand identities.
通过紫外或停流技术，在10℃的水中研究了四种具有胰岛素模拟活性的V(V)氧双过氧配合物[VO(O₂)₂L]（其中L = 草酸盐(oxa)、吡啶甲酸盐(pic)、联吡啶(bipy)、菲咯啉(phen)）将半胱氨酸氧化为胱氨酸的动力学。⁵¹V NMR光谱表明，草酸盐与吡啶甲酸盐、联吡啶和菲咯啉不同，它会发生完全的配体解离，而后三者在溶液中也能保持其配体。观察到的反应活性受配体特性的深刻影响。该过程似乎需要半胱氨酸与金属配位，然后在配位球内发生氧化。在这方面，菲咯啉和联吡啶使半胱氨酸的配位比草酸盐和吡啶甲酸盐容易得多。基于一些关于苯甲硫醇氧化的初步观察结果，也有人提出氧化过程是由电子转移步骤引发的。这一步骤的速率对于草酸盐和吡啶甲酸盐来说要高于菲咯啉和联吡啶。这些钒过氧配合物的氧化能力取决于配体性质这一观察结果，可能与它们的胰岛素模拟活性也受配体特性调节这一类似发现相匹配。
