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Myoglobin

German: Myoglobin

1 Definition

Myoglobin (Mb) is a oxygen storage protein which belongs to the family of globins. It is present in the striated muscles and heart muscles.

2 Structure

Myoglobin is a globular protein and consists of eight α-helixes in its secondary structure. Myoglobin is a protein composed of a single polypeptide chain build by 153 amino acids. The polypeptide chain is bound to a heme molecule which represents the prosthetic group of myoglobin. The heme is bound to a histidine residue at position 93 (His93 or His-F8) within the N-terminal end of the myoglobin polypeptide. If oxygen is bound to heme, the distal histidine at position 64 (called His64 or His-E7) contributes to the stabilization of the oxygen which binds to iron (Fe2+) within the heme structure.

3 Physiology

Myoglobin has a six times higher affinity to bind oxygen than hemoglobin. The hyperbolic binding curve is characteristic for myoglobin and distinguishes myoglobin from hemoglobin which has a sigmoidal binding curve. The oxygen, which is stored by myoglobin, is delivered by hemoglobin. The Bohr effect is responsible for submission of oxygen from hemoglobin to myoglobin.

4 Pathophysiology

Any situation that leads to rhabdomyolysis increases myoglobin values in the blood. Two common examples are:

An increase of myoglobin levels is an unspecific marker for myocardial ischemia but a specific one for muscle injuries.

High myoglobin levels are nephrotoxic due to free iron that is released from myoglobin during degradation. Thereby, it can lead to acute kidney failure.

5 Reference range

Myoglobin in blood serum:

  • male < 55 µg/l
  • female < 35 µg/l
  • in urin < 0.3 µg/l

6 Reference

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