Hawkinson D C, Pollack R M
Department of Chemistry and Biochemistry, University of Maryland Baltimore County 21228-5398.
Biochemistry. 1993 Jan 19;32(2):694-8. doi: 10.1021/bi00053a038.
Previous reports of a UV spectral shift upon binding of the competitive inhibitor 19-nortestosterone (1) to 3-oxo-delta 5-steroid isomerase (KSI), coupled with UV resonance Raman results, have led to the conclusion that the enone moiety is polarized to a degree similar to that produced by complete protonation and that a proton relay may be involved in the enzymatic mechanism (Austin et al., 1992). These conclusions were partly based upon interpretations of the corresponding UV spectra of 1 in aqueous acid solutions. These interpretations are shown to be inconsistent with results of deuterium exchange studies and with spectra of model systems. Consequently, there is no evidence either for an extraordinary polarization of 1 produced by binding to the active site of KSI or for a proton relay mechanism.
先前有报道称，竞争性抑制剂19-去甲睾酮（1）与3-氧代-δ5-甾体异构酶（KSI）结合时会发生紫外光谱位移，再结合紫外共振拉曼结果，得出烯酮部分的极化程度与完全质子化产生的极化程度相似，且质子传递可能参与酶促机制的结论（奥斯汀等人，1992年）。这些结论部分基于对1在酸性水溶液中的相应紫外光谱的解释。结果表明，这些解释与氘交换研究结果以及模型系统的光谱不一致。因此，没有证据表明1与KSI活性位点结合会产生异常极化，也没有证据支持质子传递机制。
