UV/VIS spectroelectrochemical investigation of catalase-peroxidase from the cyanobacterium Synechocystis PCC 6803

Catalase-peroxidases (CatGs) are prokaryotic proteins, which belong to the class I of the superfamily of plant, fungal and bacterial heme peroxidases. This class of proteins conserves the amino acid triad His/Trp/Asp in the proximal pocket and the triad Arg/Trp/His in the distal pocket. KatGs exhibit a high catalase activity and a peroxidase activity of broad specificity [1]. KatGs are the least studied class I heme peroxidases and so far only a few data are available for elucidation their characteristics and physiological roles. We investigated the redox properties of catalase-peroxidase from the cyanobacterium Synechocystis PCC 6803 through UV/VIS spectroelectrochemistry experiments. Redox potentiometric titrations were carried out at varying temperature in an anaerobic OTTLE (optically transparent thin-layer electrode) cell, set in a “non-isothermal” configuration. The reduction potential of the ferric/ferrous couple in Synechocystis KatG measured is approximately 200 mV more negative then that Mycobacterium tubercolosis KatG [2]. The reduction potential of Synechocystis KatG is in the range of the cytohrome c peroxidase and plant ascorbate peroxidase, which are other members of peroxidase superfamily I, whereas the reduction potential of Mycobacterium tubercolosis KatG is closer to that of Mn2+-dependent peroxidases.