Myoglobin

Myoglobin is one of the most important proteins in the human body. It is found in smooth and skeletal muscle tissue; where it binds oxygen and provides energy to power muscular contractions. It is an iron-oxygen binding protein found in the muscle tissue of vertebrates in general and in almost all mammals. Myoglobin is found in skeletal and cardiac muscles. It is a Hemeprotein that facilitates intracellular oxygen storage and transcellular diffusion of oxygen. Myoglobin's affinity for oxygen is higher than hemoglobin. And unlike hemoglobin which is found in the red blood cells, Myoglobin is found in muscle tissues. Myoglobin, together with the cytochromes, is responsible for the red-brown color of muscles.

In 1958, scientists Max Perutz and John Kendrew determined the 3D structure of Myoglobin by X-ray crystallography and interestingly, Myoglobin is the first protein to have its three-dimensional structure determined. In 1962, both these eminent scientists shared the Nobel prize for constructing a three-dimensional model of crystalline sperm-whale Myoglobin utilizing the technique of X-ray diffraction.

Myoglobin structure and functions

• Myoglobin transports or stores oxygen in muscles. Unlike other proteins, myoglobin is able to bind with oxygen because it contains Heme,a metal-containing prosthetic group that allows it to bind to oxygen.
  
  
• Myoglobin consists of a single polypeptide chain
  
  
• Myoglobin occurs as a monomeric heme protein
  
  
• Myoglobin contains only one heme binding sub-unit surrounded by a globular protein, containing eight alpha-helical and six non helical segments, made up of 153 amino acids.
  
  
• During the period of oxygen deprivation, oxymyoglobin releases its bound oxygen for metabolic purposes.
  

Myoglobin test results

For Men: 10 - 95 ng/ml (onset: 1-3 hrs, peak: 6-10 hrs, return to normal: 12-24 hrs)

For Women: 10 - 65 ng/ml (onset: 1-3 hrs, peak: 6-10 hrs, return to normal: 12-24 hrs)

Myoglobin Test

Myoglobin serum test may be used detect muscle damage. Myoglobin is rapidly released after muscle damage, and thus can be a useful bio marker in the early phases of muscle injury. When heart or skeletal muscle is injured, Myoglobin is released into the blood. When the damage is severe, Myoglobin levels in the blood shoot up within few hours of damage.

Excess Myoglobin in the blood is filtered by kidneys and released into the urine. And thus, severe muscle damage followed by high amounts of Myoglobin in the serum and eventually in the urine may lead to renal failure. Myoglobin levels are tested to identify the presence and timing of muscle damage. However, it cannot determine the location of muscle injury/damage. The Myoglobin blood test is also commonly used to identify a recent heart attack or acute myocardial infarction. Other sensitive markers like troponin are more commonly used today to detect heart conditions.