Cytochrome c peroxidase, or CCP,( PDB 2CYP, EC 1.11.1.5) is a water soluble ferric heme containing enzyme in the peroxidase family of enzymes that takes reducing equivalents from cytochrome c and reduces hydrogen peroxide to water.
- CCP + H2O2 + 2 reduced cytochrome c + 2H+ → CCP + 2H2O + 2 oxidized cytochrome c
It was first isolated from baker's yeast by R. A. Altschul, Abrams, and Hogness in 1940, though not to purity. The first purified preparation of yeast cytochrome c peroxidase dates to Takashi Yonetani and his preparation by ion exchange chromatography in the early 1960s. The X ray structure was the work of Thomas Poulos and coworkers in the late 1970s.
The enzyme is a monomer of molecular weight 34,000, containing 293 amino acids, and contains as well a single noncovalently bound heme b. Unusual for proteins, this enzyme crystallizes when dialyzed against distilled water. More so, the enzyme purifies as a consequence of crystallization, making cycles of crystallization an effective final purification step.
Much like catalase, the reaction of cytochrome c peroxidase proceeds through a three step process, forming first a cytochrome c peroxidase compound I and then a cytochrome c peroxidase compound II.
- CCP + ROOH → CCP-compound I + ROH + H2O
- CCP-compound I + 1e- + 1H+ → CCP-compound II
- CCP-compound II + 1e- + 1H+ → CCP
Unlike most peroxidases, CCP compound I is fairly long lived, decaying to CCP compound II with a half life at room temperature of 40 minutes to a couple hours.