title: pH titration study of cytochrome c peroxidase and apocytochrome c peroxidase.
abstract: A pH titration study of cytochrome c peroxidase and apocytochrome c peroxidase was carried out at 25 degrees C and 0.1 M ionic strength. The net charge on cytochrome c peroxidase due to proton association and dissociation varies from +32 at pH 2 to --50.2 at pH 12, while that of apocytochrome c peroxidase varies between +24.5 at pH 3 to --48 at pH 12. The apoprotein tented to aggregate below pH 3. Between pH 4 and 8, the titration behavior of both the native enzyme and the apoenzyme are consistent with the semi-empirical Linderstrøm-Lang theory. Between pH 9 and 12, the titration behavior of both the holo- and apoproteins suggest they assume a more extended conformation which reduces the electrostatic interaction charged groups on the surface. In the acid region, between pH 4 and 3, a similar transition occurs in which the protein expands 40% based on the electrostatic factor of the Linderstrøm-Lang theory.
mesh_terms: D001051:Apoenzymes; D001059:Apoproteins; D003578:Cytochrome-c Peroxidase; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008433:Mathematics; D010544:Peroxidases; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013056:Spectrophotometry, Ultraviolet; D014443:Tyrosine
chemical_list: D001051:Apoenzymes; D001059:Apoproteins; D014443:Tyrosine; D010544:Peroxidases; D003578:Cytochrome-c Peroxidase