Myoglobin which is in the oxidized ferric or hemin form. The oxidation causes a change in color from red to brown.
Ferrimyoglobin
D004798
Enzymes
Biological molecules that possess catalytic activity. They may occur naturally or be synthetically created. Enzymes are usually proteins, however CATALYTIC RNA and CATALYTIC DNA molecules have also been identified.
Biocatalyst,Enzyme,Biocatalysts
D006454
Hemoglobins
The oxygen-carrying proteins of ERYTHROCYTES. They are found in all vertebrates and some invertebrates. The number of globin subunits in the hemoglobin quaternary structure differs between species. Structures range from monomeric to a variety of multimeric arrangements.