A majority of drugs have two asymmetric molecular structures, called “enantiomers,” whose mirror images are not superimposable. The side effects of ibuprofen, which is an anti-inflammatory drug widely used in pharmaceutical products, primarily come from one of its enantiomer types. Enzymes that selectively produce enantiomers of the drug with a non-side-effect-causing molecular structure have significantly high commercial values.
The research of Meng Ting Chung, a PhD student in Prof. Kurabayashi’s group, focuses on the development of droplet-based microfluidic devices for high-throughput single-cell screening. Chung’s devices enable the research group to sort single cells encapsulated in droplets with an integrated system consisting of both microfluidic components and multi-color optics. This approach holds great promise to significantly increase the versatility, fidelity, and selectivity of fluorescence-based isolation and purification of particular cell-secreted target proteins.
Using one of the devices above, Kurabayashi group and Shanghai Jiao Tong University researchers recently discovered enzymes that produce ibuprofens with record-breaking enantiomer purity, which is 700 times higher than that of naturally existing enzymes. The research team implemented the device in an emerging biotechnology method called “directed evolution.” Directed evolution is a powerful tool for engineering proteins working as biocatalysts with desirable properties by mimicking natural evolution process in test tubes.
The device allowed the researchers to screen enzymes produced by genetically engineered E.coli mutants confined in droplet micro-reactors at a speed as high as ~107 enzyme variants per day. The enzymes were identified from among more than 5 million mutants over the course of five rounds of directed evolution. Ibuprofens produced by these enzymes are anticipated to experience a minimum chance of side effects, such as upset stomach, mild heartburn, nausea, and vomiting.
This study was published in the March 13th edition of Nature Communications titled “Efficient molecular evolution to generate enantioselective enzymes using a dual-channel microfluidic droplet screening platform.” https://www.nature.com/articles/s41467-018-03492-6