Electrochemical oxidation and reduction of PQQ using a conducting polypyrrole-coated electrode

PQQ (pyrrolo-quinoline quinone, methoxitin) is a prosthetic group of some oxidoreductases and a growth factor for microorganisms. In this study, reversible electrochemical oxidation and reduction of PQQ were performed using a conductive polypyrrole film-coated electrode. The electrochemical oxidation and reduction of PQQ on various electrodes, such as platinum, gold and glassy carbon electrodes, were found to occur irreversibly. The electrochemical behaviour of PQQ was characterized by cyclic voltammetry and differential pulse voltammetry. Electrochemically reduced PQQ (PQQH₂) was observed directly by spectrophotometry. Furthermore, PQQ was entrapped efficiently into a thin polypyrrole film by electrochemical polymerization of pyrrole. The oxidoreductive properties of entrapped PQQ were also characterized.