Discovery of a novel inhibitor of NAD(P)+-dependent malic enzyme (ME2) by high-throughput screening
作者:Yi Wen、Lei Xu、Fang-lei Chen、Jing Gao、Jing-ya Li、Li-hong Hu、Jia Li
DOI:10.1038/aps.2013.189
日期:2014.5
Malic enzymes are oxidative decarboxylases with NAD+ or NAD(P)+ as cofactor that catalyze the conversion of L-malate to pyruvate and CO2. The aim of this study was to discover and characterize a potent inhibitor of human NAD(P)+-dependent malic enzyme 2 (ME2). Recombinant human ME2-His-Tag fusion protein was overexpressed in E coli and purified with Ni-NTA resin. A high-throughput screening (HTS) assay was developed to find ME2 inhibitors. Detergent Brij-35 was used to exclude false positives. The characteristics of the inhibitor were analyzed with enzyme kinetics analysis. A thermal shift assay for ME2 was carried out to verify the binding of the inhibitor with the enzyme. An HTS system for discovering ME2 inhibitors was established with a ZⲠfactor value of 0.775 and a signal-to-noise ratio (S/N) of 9.80. A library containing 12 683 natural products was screened. From 47 hits, NPD387 was identified as an inhibitor of ME2. The primary structure-activity relationship study on NPD387 derivatives showed that one derivative NPD389 was more potent than the parent compound NPD387 (the IC50 of NPD389 was 4.63±0.36 μmol/L or 5.59±0.38 μmol/L, respectively, in the absence or presence of 0.01% Brij-35 in the assay system). The enzyme kinetics analysis showed that NPD389 was a fast-binding uncompetitive inhibitor with respect to the substrate NAD+ and a mixed-type inhibitor with respect to the substrate L-malate. NPD389 is a potent ME2 inhibitor that binds to the enzyme in a fast-binding mode, acting as an uncompetitive inhibitor with respect to the substrate NAD+ and a mixed-type inhibitor with respect to the substrate L-malate.
苹果酸酶是以NAD+或NAD(P)+为辅助因子的氧化脱羧酶,催化L-苹果酸转化为丙酮酸和二氧化碳。本研究的目的是发现并表征人类NAD(P)+依赖的苹果酸酶2(ME2)的有效抑制剂。重组人ME2-His-Tag融合蛋白在大肠杆菌中过表达,并用Ni-NTA树脂纯化。开发了高通量筛选(HTS)分析以寻找ME2抑制剂。使用洗涤剂Brij-35以排除假阳性。通过酶动力学分析分析了抑制剂的特性。对ME2进行了热转变实验,以验证抑制剂与酶的结合。建立了发现ME2抑制剂的HTS系统,Z'因子值为0.775,信噪比(S/N)为9.80。筛选了包含12683种天然产物的文库。最终,从47个命中中识别出NPD387作为ME2的抑制剂。对NPD387衍生物的初步结构-活性关系研究显示,衍生物NPD389的效能优于母化合物NPD387(NPD389在无0.01% Brij-35和有0.01% Brij-35的实验体系中的IC50分别为4.63±0.36 μmol/L和5.59±0.38 μmol/L)。酶动力学分析显示NPD389对于底物NAD+是一种快速结合的非竞争抑制剂,对于底物L-苹果酸则是一种混合型抑制剂。NPD389是一种有效的ME2抑制剂,以快速结合的方式与酶结合,作为对底物NAD+的非竞争抑制剂和对底物L-苹果酸的混合型抑制剂。