Photoswitching of peroxidase activity by position-specific incorporation of a photoisomerizable non-natural amino acid into horseradish peroxidase.

Horseradish peroxidase mutants containing L-p-phenylazophenylalanine (azoAla) at various positions were synthesized by using an Escherichia coli in vitro translation system. Among the 15 mutants examined, four mutants containing a single azoAla unit at the 6th, 68th, 142nd, and 179th positions, respectively, retained the peroxidase activity. The activity of the Phe68azoAla mutant was higher when the azobenzene group was in the cis form than in the trans form. On the contrary, the activity of the Phe179azoAla mutant disappeared when the azobenzene group was photoisomerized to the cis form, but recovered in the trans form. In the latter mutant, therefore, an on/off photoswitching of the peroxidase activity was attained.