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n. (context protein English) A small globular protein, containing a heme group, that carries oxygen to muscles


n. a hemoprotein that receives oxygen from hemoglobin and stores it in the tissues until needed


Myoglobin (symbol Mb or MB) is an iron- and oxygen-binding protein found in the muscle tissue of vertebrates in general and in almost all mammals. It is related to hemoglobin, which is the iron- and oxygen-binding protein in blood, specifically in the red blood cells. In humans, myoglobin is only found in the bloodstream after muscle injury. It is an abnormal finding, and can be diagnostically relevant when found in blood.

Myoglobin is the primary oxygen-carrying pigment of muscle tissues. High concentrations of myoglobin in muscle cells allow organisms to hold their breath for a longer period of time. Diving mammals such as whales and seals have muscles with particularly high abundance of myoglobin. Myoglobin is found in Type I muscle, Type II A and Type II B, but most texts consider myoglobin not to be found in smooth muscle.

Myoglobin was the first protein to have its three-dimensional structure revealed by X-ray crystallography. This achievement was reported in 1958 by John Kendrew and associates. For this discovery, John Kendrew shared the 1962 Nobel Prize in chemistry with Max Perutz. Despite being one of the most studied proteins in biology, its physiological function is not yet conclusively established: mice genetically engineered to lack myoglobin are viable, but showed a 30% reduction in volume of blood being pumped by the heart during a contraction. They adapted to this deficiency through natural reactions to inadequate oxygen supply ( hypoxia) and a widening of blood vessels ( vasodilation). In humans myoglobin is encoded by the MB gene.

As hemoglobin can take the forms of oxyhemoglobin (HbO), carboxyhemoglobin (HbCO), and methemoglobin (met-Hb), so can myoglobin take the forms of oxymyoglobin (MbO), carboxymyoglobin (MbCO), and metmyoglobin (met-Mb).

Usage examples of "myoglobin".

Though Spock preferred his greens to possess a distinct bite of chlorophyll, without any admixture of hemoglobin or myoglobin or whatever animal protein preceded the greens in the synthesizer, he could subsist on poorly designed food.

Sugars, acetone bodies, creatine, nitrogenous compounds, haemoglobin, myoglobin, amino acids and metabolites, uric acid, urea, urobilinogen and coproporphyrins, bile pigments, minerals, fats, and of course a great variety of psychotropic drugs: certainly all of the ones proscribed by the US Federal Bureau of Narcotics.

The other became the ancestor of all the genes that make myoglobins, a related family of proteins that work in muscles.