Catalase: Difference between revisions

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Michal Harel, Alexander Berchansky, Ann Taylor, Karsten Theis

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	Catalase is a <scene name='46/467276/Cv/2'>tetramer ~~of four polypeptide chains~~</scene>, each over 500 amino acids long. It contains <scene name='46/467276/Cv/3'>four porphyrin heme (iron) groups</scene> that allow the enzyme to react with the hydrogen peroxide. <scene name='46/467276/Cv/6'>Coordination of heme</scene> in ''E. coli'' catalase.<ref>PMID:11455600</ref> Water molecules are shown as red spheres.		Catalase is a <scene name='46/467276/Cv/2'>tetramer</scene>, each polypeptide chain is over 500 amino acids long. It contains <scene name='46/467276/Cv/3'>four porphyrin heme (iron) groups</scene> that allow the enzyme to react with the hydrogen peroxide. <scene name='46/467276/Cv/6'>Coordination of heme</scene> in ''E. coli'' catalase.<ref>PMID:11455600</ref> Water molecules are shown as red spheres.

	As hydrogen peroxide enters the active site, it interacts with the amino acids Asn147 (asparagine at position 147) and His74, causing a proton (hydrogen ion) to transfer between the oxygen atoms. The free oxygen atom coordinates, freeing the newly formed water molecule and Fe(IV)=O. Fe(IV)=O reacts with a second hydrogen peroxide molecule to reform Fe(III)-E and produce water and oxygen. The reactivity of the iron center may be improved by the presence of the phenolate ligand of Tyr357 in the fifth iron ligand, which can assist in the oxidation of the Fe(III) to Fe(IV). The efficiency of the reaction may also be improved by the interactions of His74 and Asn147 with reaction intermediates.<ref>PMID:11455600</ref> <br />		As hydrogen peroxide enters the active site, it interacts with the amino acids Asn147 (asparagine at position 147) and His74, causing a proton (hydrogen ion) to transfer between the oxygen atoms. The free oxygen atom coordinates, freeing the newly formed water molecule and Fe(IV)=O. Fe(IV)=O reacts with a second hydrogen peroxide molecule to reform Fe(III)-E and produce water and oxygen. The reactivity of the iron center may be improved by the presence of the phenolate ligand of Tyr357 in the fifth iron ligand, which can assist in the oxidation of the Fe(III) to Fe(IV). The efficiency of the reaction may also be improved by the interactions of His74 and Asn147 with reaction intermediates.<ref>PMID:11455600</ref> <br />