Thermal denaturation of cytochrome c peroxidase: pH dependence.
Upon heating cytochrome c peroxidase (ferrocytochrome c: hydrogen-peroxide oxidoreductase, EC 1.11.1.5) at pH 4 and 5, the enzyme precipitates at 41 degrees C and 51 degrees C, respectively. Incubating the enzyme at lower temperatures causes a slow dissociation of the heme from the protein. The heme precipitates, while the apoprotein remains soluble. Between pH 6 and 8, the native enzyme is converted to a low-spin ferric form upon heating. The Soret maximum shifts from 408 to 414 nm. The midpoint of this transition is pH-dependent, with a value of 46 degrees C at pH 6 decreasing to 29 degrees C at pH 8. At high temperatures the 414 nm form is converted to a species which has a 'free heme' spectrum with low absorptivity and Soret maximum at 390 nm. The midpoint temperature of this latter transition is 62 degrees C and 57 degrees C at pH 7 and 8, respectively.
Gross
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Erman
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D003578:Cytochrome-c Peroxidase / Q000378:metabolism; D006418:Heme / Q000378:metabolism; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008433:Mathematics; D010544:Peroxidases / Q000378:metabolism; D011489:Protein Denaturation; D013053:Spectrophotometry; D013816:Thermodynamics
D006418:Heme; D010544:Peroxidases; D003578:Cytochrome-c Peroxidase