Sandbox HEC: Difference between revisions

[[Image:HEC mechanism.jpg.png|thumb|400px|'''Human Erythrocyte Catalase Mechanism''' This figure illustrates the two step mechanism of catalase.  ]]

Stable forms of hydrogen peroxide are beneficial in biological reactions including hypoxia signal transduction, cell proliferation and differentiation regulation, as well as immune response mediation; however, it is toxic at high levels as free hydroxyl ions cannot be catalyzed by the body <ref name= Lennicke >PMID:26369938</ref>. Hydrogen peroxide acts to both the oxidizing and reducing agent of the iron. Catalase ultimately functions to break down hydrogen peroxide<ref name="Dash" />. This is accomplished in a two-step mechanism where the heme is first oxidized by a molecule of hydrogen peroxide to produce Compound I, a high energy oxyferryl cation radical intermediate, as well as a water molecule. Compound I is then immediately reduced by a second hydrogen peroxide molecule to produce a second molecule of water <ref name="Alfonso-Prietro" /><ref name="Diaz" />. The overall reaction results in two single-electron transfers from the iron atom of the heme group and the porphyrin from the oxoferryl radical, as well as a proton transfer from histidine. The mechanism is enthalpically driven by the distal histidine proton transfer as it is more exothermic than the electron transfers  <ref name="Alfonso-Prietro" /><ref name="Diaz" /> .