N-Ethylmaleimide

N-Ethylmaleimide is a modifier of sulfhydryl groups in proteins.^1,2 It has commonly been used to inactivate cysteine-containing enzymes in vitro. N-Ethylmaleimide inhibits prolyl endopeptidase with an IC₅₀ value of 6.3 µM.³ It alkylates cysteine 519 (Cys⁵¹⁹) in voltage-gated potassium channel 7.4 (K_v7.4) and activates K_v7.2 , K_v7.4, and K_v7.5, but not K_v7.3, in CHO cells expressing the human channels when used at a concentration of 50 µM.⁴

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1. Kawakita, M., and Yamashita, T. Reactive sulfhydryl groups of sarcoplasmic reticulum ATPase. III. Identification of cysteine residues whose modification with N-ethylmaleimide leads to loss of the Ca²⁺-transporting activity. J. Biochem. 102(1), 103-109 (1987).

2. Fatania, H.R., al-Nassar, K.E., and Thomas, N. Chemical modification of rat liver cytosolic NADP⁺-linked isocitrate dehydrogenase by N-ethylmaleimide. Evidence for essential sulphydryl groups. FEBS Lett. 322(3), 245-248 (1993).

3. Moriyama, A., Nakanishi, M., and Sasaki, M. Porcine muscle prolyl endopeptidase and its endogenous substrates. J. Biochem. 104(1), 112-117 (1988).

4. Li, Y., Gamper, N., and Shapiro, M.S. Single-channel analysis of KCNQ K⁺ channels reveals the mechanism of augmentation by a cysteine-modifying reagent. J. Neurosci. 24(22), 5079-5090 (2004).