Selection of enzymes
Enzymes have been a target for directed evolution for decades, with numerous successful trials gave hundreds of improved stability and activity enzymes to industry. Enzymes are also trickier to evolve as every reaction differs in mechanisms and complexity. It contrasts with the selection of binders where effectively only a single type of reaction is observed; every enzymatic reaction requires a unique reporter. It should ideally be selective to the studied enzyme or pathway only. In this case, the selection can be made in cells that significantly simplifies a whole protocol. Otherwise, a hybrid approach where each enzyme can get entrapped in the vesicle along with its encoding DNA, or presented on the cell surface. Alternatively each mutant can purified and individually measured in multi-well plate format.
There are numerous reviews and methodololigal articles on this inmportant topic. Here are some of recent ones: