Oxygen hemoglobin, myoglobin

Pancreatic ribonuclease Staphylococcal nuclease Peroxidases Glutathione peroxidase Cytochrome c peroxidase Oxygen carriers Myoglobin, hemoglobin Myohemerythrin, hemerythrin Hormone-binding proteins Uteroglobin Pre albumin Lectins... 

Pharmacology Iron, an essential mineral, is a component of hemoglobin, myoglobin, and a number of enzymes. Approximately two-thirds of total body iron is in the circulating red blood cell mass in hemoglobin, the major factor in oxygen transport. 

Iron occurs in every mammalian cell and is vital for life processes. It is bound to various proteins and found in blood and tissues. The iron-porphyrin or heme proteins include hemoglobin, myoglobin and various heme enzymes, such as cytochromes and peroxidases. Also, it occurs in non heme compounds, such as ferritin, siderophilin, and hemosiderin. Hemoglobin, found in the red blood cells, is responsible for transport of oxygen to the tissue cells and constitutes about two-thirds (mass) of all iron present in the human body. An adult human may contain about 4 to 6 grams of iron. 

Many proteins bind small molecules but do not catalyze a reaction of the ligand. Some examples include the binding of oxygen by myoglobin or hemoglobin and the binding of hormones and drugs by specific receptor... 

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