Proteoliposome-based capillary electrophoresis for screening membrane protein inhibitors

A method for screening of monoamine oxidase (MAO) inhibitor was carried out using capillary electrophoresis (CE) based on the interaction of MAO and its substrate kynuramine (Kyn). Bioactive proteoliposome was reconstituted by liposome and MAO and then was applied as the pseudostationary phase (PSP) of CE to mimic the interaction between the enzyme and its substrate. N-prolmrgyl-R-2-heptylamine (R-2-HPA) and rasagiline [N-propargyl-1-(R)- aminoindan], which are two kinds of MAO inhibitors, were added into the running buffers containing proteoliposome. The results showed that the relative migration time ratio (RMTR ×10^-1) values of Kyn were enhanced from 8.88 to 9.31 with an increase of the concentrations of rasagiline from 10^-6 to 1 mM. However, the RMTR values of Kyn were enhanced from 8.83 to 9.14 with an increase of the concentrations of R-2-HPA from 10^-6 to 1 mM. The RMTR value of Kyn in the presence of rasagiline was larger than that in the presence of R-2-HPA when rasagiline and R-2-HPA were at the same concentration. The results indicated that the interaction between Kyn and MAO was weakened with the increase of the inhibitors. In addition, the results of offline incubation showed that the inhibitions of rasagiline were 100.0, 72.1, 51.8 and 5.4% at the concentration of 1, 10^-2, 10^-4 and 10^-6 mM; moreover, the inhibitions of R-2-HPA were 70.0, 44.9, 4.1 and 0.9% at the concentrations of 1, 10^-2, 10^-4 and 10^-6-6 mM. The inhibition efficiency of rasagiline was stronger than that of R-2-HPA at the same concentration. Additionally, the interaction between Kyn and liposome was also investigated. This newly developed method might provide a potential tool for screening MAO inhibitor.