Monitoring Methionine Decarboxylase by a Supramolecular Tandem Assay

Abstract

Methionine is an essential amino acid involved in many physiological and pathological processes. Methionine starvation caused by methionine decarboxylase (MetDC) degradation becomes a promising strategy for cancer treatment. Multistep colorimetric method, the present approach to monitor the MetDC activity, possesses drawbacks of the complicated process, low accuracy, and poor anti-interfer-ence due to indirect detection. Herein, we report a facile and easy-to-use supramolecular tandem assay (STA) with the cucurbit[7]uril and acridine orange reporter pair for the direct and real-time monitoring of MetDC activity. This strategy not only provides a feasible method for enzymatic activity detection but also establishes the capability of inhibitor screening.

A Label‐Free and Continuous Fluorescence Detection for L–DOPA Decarboxylase Activity Based on Supramolecular Tandem Assay

“…To be eligible for a tandem assay, a good reporter pair should meet the following conditions: i) appreciable complexation‐induced fluorescence signal of the indicator, ii) relatively strong binding ability of the supramolecular host with the indicator, and iii) substantial differences in binding affinities between the substrate and product with the host. The CB7•AO reporter pair exhibited binding differences to the amines and amino acids, [19] which has been demonstrated to be suitable for establishing STA based on amino acid decarboxylases [11b] . First, we obtained the binding affinity of CB7 with AO (association constant, K a =(5.22±0.29)×10 4 M −1 ) by direct fluorescence titrations (Figures 1a, 1b and S1), which was similar to previous results [11b] .…”

“…The CB7•AO reporter pair exhibited binding differences to the amines and amino acids, [19] which has been demonstrated to be suitable for establishing STA based on amino acid decarboxylases [11b] . First, we obtained the binding affinity of CB7 with AO (association constant, K a =(5.22±0.29)×10 4 M −1 ) by direct fluorescence titrations (Figures 1a, 1b and S1), which was similar to previous results [11b] . The strong inclusion of CB7⋅AO complex led to a dramatic complexation‐induced fluorescence change upon AO.…”