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Myoglobin

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An Overview of Myoglobin and its Functions

IVSAT 2024

Myoglobin, symbolized by Mb is an oxygen and iron-binding protein that is found in the skeletal and cardiac muscle tissue of almost all mammals and vertebrates. Myoglobin is a distant relative of hemoglobin. When compared to the latter, myoglobin proves to have a higher affinity towards oxygen. It also doesn’t have a cooperative type of binding with oxygen, unlike hemoglobin.


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In human beings, myoglobin can be found in the bloodstream after they suffer from any kind of muscle injury. A myoglobin test confirms whether the oxygen-binding properties in organisms are high or not.


What is Myoglobin?

The three-dimensional structure of myoglobin was first revealed through the process of X-ray crystallography. John Kendrew along with his associates reported this achievement in the year 1958. Due to this achievement, Kendrew shared the Nobel Prize in 1962 with Max Perutz. In spite of being one of the most studied protein types, the functions of myoglobin are not conclusive yet.


It has been seen that a higher concentration of myoglobin found in the muscle cells can allow organisms to hold their breath for longer durations of time. The organisms with diving properties such as seals and whales tend to have an abundance of myoglobin in their blood. The main locations for myoglobin are found to be in Type I, Type II A, and Type II B muscles. In human beings, myoglobin can be encoded with the gene MB. Myoglobin can take multiple forms such as carboxymyoglobin (MbCO), metmyoglobin (met-Mb), and oxymyoglobin (MbO2).


Myoglobin Vs Hemoglobin

Just like hemoglobin, myoglobin can be described as a protein with a cytoplasm that will bind itself to the oxygen molecules using a heme group. However, there are some differences that are mentioned below.


Myoglobin

Hemoglobin

Myoglobin consists of only one.

Hemoglobin has four different globulin groups.

Myoglobin has a higher affinity towards oxygen.

Hemoglobin has less affinity towards oxygen when compared to myoglobin.

Myoglobin acts as a storage for oxygen

Hemoglobin plays a role in transporting oxygen

Myoglobin doesn’t have cooperative binding with oxygen.

Hemoglobin has a cooperative binding with oxygen.

 

Role of Myoglobin Present in Bodies to Test Diseases

The amount of myoglobin present in the damaged muscle tissue is very high. While the released myoglobin is very high, it is filtered by the kidneys. However, the content of myoglobin is toxic to the renal tubular epithelium and hence it can cause acute injuries to the kidney.


One important thing to keep in mind is that myoglobin in itself is not toxic, since it is a protoxin. However, the ferrihemate portion that can be dissociated from the myoglobin content in certain acidic environments can be toxic. Hence, in order to determine the myoglobin in urine, the doctor might ask for a myoglobin test when you go for a checkup.


Myoglobin proves to be a very sensitive marker for certain injuries in the muscles. Thus, it becomes a potential marker for problems such as heart attack in people who have regular chest pain. However, higher levels of myoglobin don’t have much specificity in the case of Acute Myocardial infarction or AMI. Hence, factors such as cardiac troponin, CK-MB, ECG, and some other clinical signs should also be taken into consideration in order to make an accurate diagnosis.


Myoglobin Function: What does it do?

Myoglobin is a protein that is found in the muscle cells of vertebrates. It can act as a reservoir for Oxygen in the body. It also acts as a supplier of oxygen to the muscles that act in the body. Certain diving mammals that include whales, as well as seals, are able to submerge themselves inside water for a long period of time due to the fact that they have higher levels of myoglobin in their bodies when compared to other animals. So, what is it that makes myoglobin so special? Well, it allows your body to have its very own supply of blood, just like hemoglobin. With proper myoglobin normal range, a person will have a higher level of oxygen supply in their body.


Some Interesting Facts About Myoglobin

  • The structure of myoglobin is globular. It has a molecular weight of 16,700.

  • Myoglobin is monomeric and has a residue of 153 amino acids.

  • There are eight α-helix that are connected in myoglobin to bind oxygen to itself.

  • Out of all the amino acids, about 121 are situated on the different helical regions and the remaining 32 are distributed over all the non-helical areas.

  • Myoglobin has an overall molecular dimension of 45 X 35 X 25 Ao.

  • The prosthetic heme present in myoglobin provides the function of carrying different molecules of oxygen to the tissues.


Conclusion

Myoglobin is an important component that facilitates the supply of oxygen to different muscles and tissues. It is an active component, much like hemoglobin that decides the level of oxygen in the bodies of vertebrates.

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FAQs on Myoglobin

1. What is Myoglobin?

Myoglobin is a protein that is oxygen and iron-binding in nature. Myoglobin is found in the cardiac and skeletal tissues of the bodies of different vertebrates. Just like hemoglobin, it helps in supplying oxygen to the different body parts of animals. However, there is a difference between hemoglobin and myoglobin. While hemoglobin acts as a transportation service for oxygen, myoglobin’s main function is to store the oxygen and provide it to the muscles that are in action. Higher levels of myoglobin are found in mammals such as whales and seals. With such a high level of myoglobin, these mammals are able to hold their breath underwater for a very long time.

2. What is a Myoglobin Test?

The myoglobin test is used in order to determine the amount of this particular protein in the blood of a person. This test can be used in order to determine certain conditions that are caused by any damage to the muscles. It is known that all the myoglobin can be found in the skeletal as well as heart muscles. Being an excellent market for muscle injuries, it can also detect heart diseases as well. Apart from that, a doctor might recommend a test to check the amount of myoglobin in urine so that they can analyze the person’s risk for developing any diseases in the kidneys.   


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