Monitoring Methionine Decarboxylase by a Supramolecular Tandem Assay.

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-interference 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.

Improving the System Performance of the Asymmetric Biosynthesis of d-Pantoic Acid by Using Artificially Self-Assembled Enzymes in Escherichia coli.

d-Pantoic acid (d-PA) is an important chiral precursor of a broad range of biologically active compounds. The asymmetric synthesis of d-PA through reductase coupling with NADPH regeneration systems is highly promising, but the process is restricted by expensive cofactor consumption and low cofactor recycling frequency. Here, an effective construction of self-assembled ketopantoic acid reductase and glucose dehydrogenase via protein-peptide interaction of PDZ domain and PDZ ligand was established. The self-assembled enzymes exhibited highly ordered two-dimensional threadlike macromolecular structures with improved cofactor regeneration. Furthermore, the bioconversion with whole-cell catalysis showed that the robustness and efficiency of the system with self-assembled enzymes were significantly higher than those of the unassembled enzymes. This study provides a strategy for the effective asymmetric biosynthesis of d-PA with a trace amount of cofactor and shows potential for industrial applications.