Electrocatalytic Properties of Immobilized Heme Proteins: Basic Principles and Applications

Abstract

Heme proteins encompass redox enzymes, electron transferases, and species for dioxygen transport and storage. Upon immobilization on a conductive surface, heme proteins can accomplish bioelectrocatalysis. In this process, they carry out oxidation or reduction of substrates at a solid electrode acting as electron acceptor or donor, respectively, thanks to electron transfer processes occurring at the interphase. The efficiency of bioelectrocatalysis depends on the electrical communication of the protein with the electrode surface, retention of protein structure upon adsorption and accessibility of the substrate to the active site. This Minireview outlines the main factors affecting bioelectrocatalysis by adsorbed heme proteins, highlights open issues, and summarizes recent advances in the field.

Electron Transfer and Electrocatalytic Properties of the Immobilized Met80Ala Cytochrome c Variant in Dimethylsulfoxide

“…Exploitation of native and engineered enzymes and proteins as core components of hybrid inorganic/biological interfaces for applications in biosensing and biocatalysis has grown considerably in the last decades. [1][2][3][4][5][6][7][8][9][10] These devices, however, are in general meant to operate in aqueous solution. Extending the use of these systems to mixed water/organic solvents or even pure organic solvents would open up the prospect of applying biocatalytic processes and protein-based recognition systems to non-conventional substrates, soluble only in organic solvents.…”

How to Turn an Electron Transfer Protein into a Redox Enzyme for Biosensing

“…The heme group is the most abundant metal cofactor in living organisms and is involved in many different biological functions, from O 2 binding and transport, to redox catalysis, from electron shuttling, to molecular sensing [ 1 , 2 , 3 , 4 ]. The reason for this large variety of functions is the chemical versatility of the heme center the reactivity of which is modulated and fine-tuned by the protein matrix, which may control the iron atom axial coordination and spin state, the accessibility to solvent and exogenous molecules, and the polarity of the surrounding environment [ 3 , 4 , 5 , 6 , 7 ].…”

“…The multiplicity of physiological roles and the ease of isolation, genetic manipulation, and physico-chemical characterization have made electrode-immobilized native and mutated heme proteins the species of choice for the development of bio(in)organic interfaces for (bio)sensing and catalysis [ 5 , 6 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Exploiting the direct adsorption or covalent attachment of the redox-active protein on the electrode surface proved to be an attractive and promising approach, leading to the development of efficient third-generation amperometric biosensors for substrates of clinical and industrial relevance (O 2 , H 2 O 2 , NO 2 − ) [ 5 , 6 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Its main drawback consists in the immobilization-induced protein unfolding and inactivation, which may severely hamper the electrochemical and electrocatalytic responses [ 5 , 6 ].…”

“…Exploiting the direct adsorption or covalent attachment of the redox-active protein on the electrode surface proved to be an attractive and promising approach, leading to the development of efficient third-generation amperometric biosensors for substrates of clinical and industrial relevance (O 2 , H 2 O 2 , NO 2 − ) [ 5 , 6 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Its main drawback consists in the immobilization-induced protein unfolding and inactivation, which may severely hamper the electrochemical and electrocatalytic responses [ 5 , 6 ]. This is particularly relevant for globins, peroxidases, catalases, and cytochrome P450, since their heme b is not covalently bound to the protein matrix and can be partially or completely released upon protein denaturation, generating electrochemical responses due to non-native conformers or freely-diffusing heme groups in solution [ 5 , 16 , 17 , 18 ].…”

Electrochemical Characterization and Bioelectrocatalytic H2O2 Sensing of Non‐Symbiotic Hexa‐Coordinated Sugar Beet Hemoglobins

“…Unambiguous to all living aerobic organisms, heme proteins play a vital role in oxygen transport, activation, respiration, drug detoxification, signal transduction and sensing of ligands both toxic and crucial to organisms’ survival . Redox activity of heme proteins had promoted their bioelectrochemical applications, and they represent now one of the major group of biocatalysts whose heterogeneous electron transfer (ET) reactions with electrodes are used in electroanalysis, biofuel cell development, and bioelectrochemical transformations …”