Monoamine oxidase inhibitor screening by proteoliposome capillary electrophoresis

In this study, a new strategy for screening of enzyme inhibitors based on the interaction between enzyme and substrate was established. The bioactive proteoliposome reconstituted by monoamine oxidase (MAO) and liposome was added in the running buffers of capillary electrophoresis (CE) as pseudostationary phase to simulate the interaction between MAO and its substrate kynuramine (Kyn). The results showed that the relative migration time ratio (RMTR) of Kyn decreased obviously with increase of the proteoliposome, indicating strong interaction between proteoliposome and Kyn. After adding MAO inhibitors into the running buffers containing proteoliposome, the decline of the RMTR value of Kyn became slower. This occurred because MAO was inhibited to some degree by the inhibitors, weakening the interaction between MAO and Kyn. However, adding compounds which do not inhibit MAO activity into the running buffers did not affect the RMTR of Kyn obviously. The results obtained demonstrate that the method developed could characterize the inhibition of MAO inhibitors. Compared with traditional inhibitor screening methods, it does not need incubation outside the column to complete the enzyme catalytic reaction, so analysis is faster and less sample is consumed. With further development, the method might be chosen as a useful tool for screening of membrane protein inhibitors and identification of proteins associated with various diseases.