Structural and Functional Properties of Heme-containing Peroxidases: a Resonance Raman Perspective for the Superfamily of Plant, Fungal and Bacterial Peroxidases
The heme-containing peroxidases of the plant peroxidase superfamily have been the subject of extensive studies to gain a complete understanding of their structure and function properties. Spectroscopic techniques have been fundamental to the comprehension of peroxidase function under physiological conditions. Resonance Raman spectroscopy has assumed a particularly important role due to its extreme sensitivity to alterations in the surroundings of the heme, which makes it an ideal tool for studying molecular interactions at the peroxidase active sites. In combination with site-directed mutagenesis and X-ray structural data, it has given insight into the influence exerted on protein architecture in the vicinity of the active site by key amino acids and furnished critical information on subtle structural features important for protein flexibility, functionality and stability. The mutation of key catalytic residues on both the distal and proximal sides of the heme cavity not only revealed their roles in the reaction mechanism of peroxidases, but also demonstrated that in peroxidases there are common structural mechanisms which facilitate communication between the two sides of the heme cavity and highlighted the importance of long range interactions in maintaining the functional properties of the heme. The overwhelming success of this approach using the combination of site-directed mutagenesis together with spectroscopic techniques and X-ray structural data to unveil detailed aspects of the structure–function relationships of heme peroxidases, firstly in the pioneering studies on yeast cytochrome c peroxidase then for other peroxidases, has led to its subsequent widespread general application in the characterization of heme proteins.