N-Ethylmaleimide (NEM) is derived from maleic acid and can alkylate free sulfhydryl groups. It is a protein sulfhydryl modifier that can be used to modify cysteine residues in proteins and peptides [1]. N-Ethylmaleimid inhibits prolyl endopeptidase with an IC50 value of 6.3 μM [2]. N-Ethylmaleimid is an irreversible inhibitor of all cysteine peptidases, and alkylation occurs at the active site thiol group [3]. N-Ethylmaleimid has also been used as an inhibitor of deubiquitinase [4].
In vitro, treatment of vascular smooth muscle cells with N-Ethylmaleimid (20 μM) effectively inhibited the phosphorylation of Akt Ser-473, Akt Thr-308, p70S6K, ribosomal protein S6, 4E-BP1, BAD and FKHR-L1 stimulated by platelet-derived growth factor-BB (PDGF-BB) [5].
In vivo, N-Ethylmaleimid (10 mg/kg, subcutaneous injection) treatment of male Wistar rats with acute gastric ulcer induced by anhydrous ethanol injection increased the lesion area of acute gastric ulcer and weakened the gastroprotective effect of momordica charantia Ic[6].
References:
[1] Robotham A C, Kelly J F. Detection and quantification of free sulfhydryls in monoclonal antibodies using maleimide labeling and mass spectrometry[C]//MAbs. Taylor & Francis, 2019, 11(4): 757-766.
[2]Moriyama A, Nakanishi M, Sasaki M. Porcine muscle prolyl endopeptidase and its endogenous substrates[J]. The Journal of Biochemistry, 1988, 104(1): 112-117.
[3]Schirmeister T. New peptidic cysteine protease inhibitors derived from the electrophilic α-amino acid aziridine-2, 3-dicarboxylic acid[J]. Journal of medicinal chemistry, 1999, 42(4): 560-572.
[4]Sarkar K, Sadhukhan S, Han S S, et al. SUMOylation-disrupting WAS mutation converts WASp from a transcriptional activator to a repressor of NF-κB response genes in T cells[J]. Blood, The Journal of the American Society of Hematology, 2015, 126(14): 1670-1682.
[5]Yellaturu C R, Bhanoori M, Neeli I, et al. N-Ethylmaleimide inhibits platelet-derived growth factor BB-stimulated Akt phosphorylation via activation of protein phosphatase 2A[J]. Journal of Biological Chemistry, 2002, 277(42): 40148-40155.
[6]Matsuda H, Li Y, Yoshikawa M. Roles of capsaicin-sensitive sensory nerves, endogenous nitric oxide, sulfhydryls, and prostaglandins in gastroprotection by momordin Ic, an oleanolic acid oligoglycoside, on ethanol-induced gastric mucosal lesions in rats[J]. Life Sciences, 1999, 65(2): 27-32.
N-乙基马来酰亚胺（N-Ethylmaleimide；NEM）衍生于马来酸，能烷基化游离巯基，是一种蛋白质巯基修饰剂，可用于修饰蛋白质和多肽中的半胱氨酸残基[1]。N-Ethylmaleimid对脯氨酰内肽酶有抑制作用，IC50值为6.3μM[2]。N-Ethylmaleimide是所有半胱氨酸肽酶的不可逆抑制剂，烷基化发生在活性位点硫醇基团处[3]。N-Ethylmaleimid也被用作去泛素酶的抑制剂[4]。
在体外，N-Ethylmaleimid（20 μM）处理血管平滑肌细胞，可有效抑制血小板衍生生长因子-BB（PDGF-BB）刺激的Akt Ser-473、Akt Thr-308、p70S6K、核糖体蛋白S6、4E-BP1、BAD和FKHR-L1磷酸化[5]。
在体内，N-Ethylmaleimid（10mg/kg，皮下注射）处理无水乙醇注射致急性胃溃疡雄性Wistar大鼠，增加了急性胃溃疡的病变面积并减弱了苦瓜素Ic的胃保护作用[6]。