Evolving enzymatic electrochemistry with rare or unnatural amino acids

Proper orientation of oxidoreductases on electrodes is important for efficient electron transfer in bioelectrochemical studies. Site-directed mutagenesis confers the ability to control the orientation of enzymes on electrodes in addition to modifying enzyme catalytic properties and understanding native electron transfer mechanisms and protein–protein interactions. Although numerous improvements have been achieved in the site-directed immobilization of enzymes, they are limited to the use of the 20 “standard” amino acids of the protein. This opinion considers the utilization of unnatural amino acids (UAAs) to introduce unique functional groups to proteins for their site-specific immobilization and subsequent enzymatic electrochemistry studies. Moreover, the importance of the site-specific incorporation of selenocysteine is described due to its potential to improve/alter the electrochemical properties.