Moebius F F, Reiter R J, Bermoser K, Glossmann H, Cho S Y, Paik Y K
Institut für Biochemische Pharmakologie, Universität Innsbruck, Peter Mayr Str. 1, A-6020 Innsbruck, Austria.
Mol Pharmacol. 1998 Sep;54(3):591-8. doi: 10.1124/mol.54.3.591.
Sterol Delta8-Delta7 isomerases (SIs) catalyze the shift of the double bond from C8-9 to C7-8 in the B-ring of sterols. Surprisingly, the isoenzymes in fungi (ERG2p) and vertebrates [emopamil binding protein (EBP)] are structurally completely unrelated, whereas the sigma1 receptor, a mammalian protein of unknown function, bears significant similarity with the yeast ERG2p. Here, we compare the drug binding properties of SIs and related proteins with [3H]ifenprodil as a common high affinity radioligand (Kd = 1.4-19 nM), demonstrating an intimate pharmacological relationship among ERG2p, sigma1 receptor, and EBP. This renders SIs a remarkable example for structurally diverse enzymes with similar pharmacological profiles and the propensity to bind drugs from different chemical groups with high affinity. We identified a variety of experimental drugs with nanomolar affinity for the human EBP (Ki = 0.5-14 nM) such as MDL28815, AY9944, triparanol, and U18666A. These compounds, as well as the fungicide tridemorph and the clinically used drugs tamoxifen, clomiphene, amiodarone, and opipramol, inhibit the in vitro activity of the recombinant human EBP (IC50 = 0.015-54 microM). The high affinity of the human EBP for 3H-tamoxifen (Kd = 3 +/- 2 nM) implies that the EBP carries the previously described microsomal antiestrogen binding site. Interactions of the EBP with structurally diverse lipophilic amines suggest that novel compounds of related structure should be counterscreened for inhibition of the enzyme to avoid interference with sterol Delta8-Delta7 isomerization.
甾醇δ8-δ7异构酶（SIs）催化甾醇B环中双键从C8-9位转移至C7-8位。令人惊讶的是，真菌中的同工酶（ERG2p）与脊椎动物中的[伊莫帕明结合蛋白（EBP）]在结构上完全不相关，而功能未知的哺乳动物蛋白σ1受体与酵母ERG2p具有显著相似性。在此，我们以[3H]ifenprodil作为常见的高亲和力放射性配体（Kd = 1.4-19 nM），比较了SIs及相关蛋白的药物结合特性，证明了ERG2p、σ1受体和EBP之间存在密切的药理学关系。这使SIs成为具有相似药理学特征且倾向于高亲和力结合不同化学基团药物的结构多样酶的一个显著例子。我们鉴定出了多种对人EBP具有纳摩尔亲和力（Ki = 0.5-14 nM）的实验性药物，如MDL28815、AY9944、曲帕拉醇和U18666A。这些化合物，以及杀真菌剂十三吗啉和临床使用的药物他莫昔芬、氯米芬、胺碘酮和奥匹哌醇，均抑制重组人EBP的体外活性（IC50 = 0.015-54 μM）。人EBP对3H-他莫昔芬的高亲和力（Kd = 3 ± 2 nM）表明EBP具有先前描述的微粒体抗雌激素结合位点。EBP与结构多样的亲脂性胺类的相互作用表明，应筛选相关结构的新型化合物以抑制该酶，避免干扰甾醇δ8-δ7异构化。
