Recent trends in enzyme engineering aiming to improve bioelectrocatalysis proceeding with direct electron transfer

Among the known types of electrochemical biosensors, the third generation based on the ability of some enzymes to direct electron transfer (DET) is the most promising one. The enzyme property to DET is depending on its capability to electron transfer from enzymatically reduced built-in native cofactor (flavin mononucleotide, flavin adenine dinucleotide, pyrroloquinoline quinone, or heme) to a conductive surface directly for single cofactor enzymes or through a native structural electron acceptor (heme or copper-containing prosthetic groups) for multicofactor enzymes. Thus, there are two possibilities to use such type enzymes: to find a natural source of the enzyme with these properties; or to construct the recombinant chimeric analogs using the gene-engineering techniques. The modern molecular genetics opens the possibility to be independent of million-year natural evolution and engineer the specific enzymes for scientific and technological needs. This brief review is focused mostly on the recent publications on application of DET-capable engineered enzymes for the third-generation electrochemical biosensors.