Investigation of thermal unfolding process of cyanic adduct of horseradish peroxidase by fourier transform infrared and circular dichroism spectrometry

摘要

Horseradish peroxidase (HRP, EC 1.11.1.7) is the most widely studied member of heme peroxidase family. The X-ray structure of HRP has already been solved. The structural features of HRP include Ca~(2+) binding sites proximal and distal to the heme, four disulfide bridges, and a number of N-glycosylation sites. These and an extensive hydrogen-bonding network may aid in stabilization of the secondary and/or tertiary structure of the enzyme. The iron of the heme prosthetic group of HRP was found to be pentacoordinated. The Ca~(2+) site is seven-coordinate, and the ligands are carbonyl and side chain oxygens. Thermal stability of native HRP was also investigated by FTIR and CD. The nature of the inhibition of HRP and cytochrome c oxidase by cyanyl radical was also investigated recently. However, the detailed thermal unfolding process of cyanic adduct of HRP is still unclear.