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Myoglobin is a red-coloured pigment that is responsible for storing and carrying oxygen in the muscles of vertebrates, including humans. It is an iron-containing protein that is found predominantly in the cardiac and skeletal muscles, with particularly high concentrations in the muscles of diving mammals such as whales and seals. Myoglobin's ability to bind and release oxygen is essential for supplying oxygen to the muscle tissues and facilitating oxygen diffusion, making it a crucial component of the body's oxygen transport system.
| Characteristics | Values |
|---|---|
| Name | Myoglobin |
| Symbol | Mb or MB |
| Type | Protein |
| Function | Supplies oxygen to muscle |
| Found in | Cardiac and skeletal muscle tissue of vertebrates and almost all mammals |
| Properties | Sensitive marker for muscle injury, higher affinity for oxygen than hemoglobin, ability to bind and release oxygen |
| Structure | Single polypeptide chain with one oxygen binding site, eight alpha helices connected by loops, 154 amino acids |
| Color | Red |
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What You'll Learn
Myoglobin is an iron-containing protein
Myoglobin contains a heme prosthetic group that can reversibly bind to oxygen. The body uses it as an oxygen storage protein in muscle. It is able to bind and release oxygen depending on the oxygen concentration in the cell. Its primary function is to supply oxygen to myocytes and muscle. Myoglobin also functions in the hemostasis of nitric oxide and plays a role in the detoxification of reactive oxygen species.
The molecule contains a heme prosthetic group, which includes a porphyrin ring iron ion. The heme-bound Fe cation can exist in the 2+ (reduced) or 3+ (oxidized) state. The iron ion itself interacts with six different ligands, one of which serves as the binding site for oxygen. This binding site can also function to bind other potential molecules, including CO and NO.
Myoglobin is a member of the globin superfamily of proteins, which also includes hemoglobin. It consists of eight alpha helices connected by loops. Human myoglobin contains 154 amino acids. Myoglobin is the reason for the red colour of the muscle of most vertebrates and red meat.
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It's found in cardiac and skeletal muscles
Myoglobin is an iron- and oxygen-binding protein found in the cardiac and skeletal muscle tissue of vertebrates and almost all mammals. It is a member of the globin superfamily of proteins, which also includes haemoglobin.
Myoglobin is a single polypeptide chain with one oxygen-binding site. It contains a heme prosthetic group that can reversibly bind to oxygen. The body uses it as an oxygen storage protein in muscle. Its primary function is to supply oxygen to myocytes. Myoglobin also functions in the hemostasis of nitric oxide and plays a role in the detoxification of reactive oxygen species.
Myoglobin occurs in the highest concentration in the striated muscles of vertebrates, specifically in the cytoplasm of cardiac myocytes and the sarcoplasm of oxidative skeletal muscle fibres. It is also present in much lower concentrations in smooth muscle, endothelial tumour cells, and even tumour cells.
Myoglobin is a sensitive marker for muscle injury, making it a potential marker for heart attacks in patients with chest pain. It is also useful in evaluating infarct size and reperfusion.
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Myoglobin supplies oxygen to muscles
Myoglobin is an iron- and oxygen-binding protein found in the cardiac and skeletal muscle tissue of vertebrates and almost all mammals. It is encoded by the MB gene in humans. Myoglobin is a single polypeptide chain with one oxygen binding site, which results in different binding kinetics to oxygen compared to other proteins.
Myoglobin contains hemes, pigments responsible for the colour of red meat. The degree of oxidation of the myoglobin determines the colour of the meat. In fresh meat, the iron atom is in the ferrous (+2) oxidation state bound to an oxygen molecule (O2). When cooked, the meat turns brown as the iron atom loses an electron and enters the ferric (+3) oxidation state.
Myoglobin's primary function is to supply oxygen to muscles. It achieves this by releasing its oxygen supply to the mitochondria that make up the respiratory chain, helping the myocytes meet their high energy demands. Myoglobin also serves as an oxygen reservoir in muscles, allowing organisms with high concentrations of myoglobin in muscle cells to hold their breath for longer. Diving mammals such as whales and seals have particularly high levels of myoglobin in their muscles, enabling them to remain submerged for extended periods.
Myoglobin is also involved in the detoxification of reactive oxygen species and the hemostasis of nitric oxide. It is necessary for the decomposition of bioactive nitric oxide to nitrate, enhancing mitochondrial respiration.
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It binds and releases oxygen
Myoglobin is a red-coloured pigment found in the muscles of vertebrates and almost all mammals. It is an iron- and oxygen-binding protein that serves as an oxygen reservoir in muscle cells. Myoglobin can bind and release oxygen depending on the oxygen concentration in the cell. It has a higher affinity for oxygen compared to hemoglobin and can efficiently extract oxygen from the blood.
The presence of the heme group in myoglobin allows it to bind and release oxygen. The heme group contains a porphyrin ring with an iron atom at its centre. This iron atom can exist in the ferrous (+2) or ferric (+3) oxidation state. In fresh meat, the iron atom is in the ferrous (+2) oxidation state and is bound to an oxygen molecule (O2). When meat is cooked well done, the iron atom transitions to the ferric (+3) oxidation state, losing an electron and resulting in a brown colour.
The binding of oxygen (O2) to myoglobin causes a substantial structural change at the iron (Fe) centre. The Fe centre shrinks in radius and moves into the centre of the N4 pocket. This oxygen-binding process induces "spin-pairing," leading to a change in the spin state of the iron atom. The interaction between the distal imidazole group of myoglobin and the oxygen molecule encourages the binding of O2.
Myoglobin plays a crucial role in supplying oxygen to the muscles, particularly during periods of high metabolic demand. It releases its oxygen supply to the mitochondria in the muscle cells, facilitating oxygen diffusion and enhancing mitochondrial respiration. The presence of high concentrations of myoglobin in muscle cells enables organisms, such as diving mammals, to hold their breath for extended periods. Myoglobin also has enzymatic functions and plays a role in the detoxification of reactive oxygen species.
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Myoglobin is a marker for muscle injury
Myoglobin is an iron- and oxygen-binding protein found in the cardiac and skeletal muscle tissue of vertebrates and almost all mammals. It is encoded by the MB gene in humans. Myoglobin is a sensitive marker for muscle injury, making it a potential marker for heart attacks in patients with chest pain.
Myoglobin is released into the blood when heart or skeletal muscle is injured. Blood levels of myoglobin can rise very quickly with severe muscle damage and can be measured within a few hours following an injury. It is markedly more sensitive than CK or CK-MB activities within 4 hours after the onset of chest pain. It is still commonly used as an early cardiac biomarker in clinical practice.
Myoglobin is filtered from the blood by the kidneys and is released into the urine. Sometimes, a urine test is used to evaluate myoglobin levels in people who have had extensive damage to their skeletal muscles (rhabdomyolysis). Urine myoglobin levels reflect the degree of muscle injury.
Myoglobin is also present in much lower concentrations in smooth muscle, endothelial, and even tumour cells. However, myoglobin's role as a marker for disease is limited. Its concentration is elevated in renal insufficiency but displays excellent early sensitivity, increasing more rapidly than troponin and CK. Despite this, the presence of myoglobin in skeletal muscle limits its diagnostic specificity.
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Frequently asked questions
Myoglobin is the name of the pigment that traps oxygen in muscles.
Myoglobin is an iron- and oxygen-binding protein found in the cardiac and skeletal muscle tissue of vertebrates and almost all mammals.
Myoglobin's primary function is to supply oxygen to muscles. It does this by releasing its oxygen supply to the mitochondria.
Myoglobin is a red pigment. It is responsible for the colour of red meat.
When heart or skeletal muscles are injured, myoglobin is released into the blood. A myoglobin blood test can be used to detect muscle damage.
