In biochemistry, non-heme iron proteins describe families of enzymes that utilize iron at the active site but lack heme cofactors. Iron-sulfur proteins, including those that are enzymes, are not included in this definition. By tradition, non-heme iron enzymes refers to those involved in oxygen activation, such as those described below. Some non-heme iron proteins contain one Fe at their active sites, others have pairs of Fe centers:
Many mono-Fe proteins are alpha-ketoglutarate-dependent hydroxylases. Major examples are the lipoxygenases, isopenicillin N synthase, protocatechuate 3,4-dioxygenase, deacetoxycephalosporin-C synthase, and aromatic amino acid hydroxylases.
Diiron enzymes include hemerythrin, some ribonucleotide reductases, and some methane monooxygenases, Some of these active sites are mixed valence (Fe(II)Fe(III)) and some are diferrous (Fe(II)Fe(II)).
Other non-heme iron proteins purple acid phosphatases ferritin. Iron-binding proteins
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