The protein thrombin is found in the blood of humans. It is a serine protease like tyrpsin and chymotrypsin. A serine protease is a protein cutting enzyme that uses a serine amino acid to perform the cleavage. It has selective digestion, so that it does not digest other important proteins in the blood.
Thrombin plays an important role in blood clotting. When humans are wounded the body will build a temporary block to give the surrounding tissues a chance to repair the wound. When the skin is cut and blood flows to cells that do not normally come in contact with blood, it signals the body. These cells are called tissue factor. Tissure factor will then activate Factor VII and Factor X. These factors then activate thrombin, which translates the signal into action. Thrombin clips a little piece of the large protein fibrinogen. Fibrinogen assembles into large stringy networks that trap the blood cells forming a scab that blocks the wound.
Since blood clotting can pose potential risks such as heart attack and strokes, it is carefully regulated. It's built as an inactive precursor that has several extra domains that are clipped off when activated. The thrombin molecule consists of calcium ions that bind to modified glutamate amino acids causing a positive charge and tether to the surfaces of blood vessels. This prevents thrombin from spreading everywhere once activated. The activation of thrombin only last several seconds to limit the clot to the area of damage.
To find out more information on thrombin please visit http://www.pdb.org/pdb/101/motm.do?momID=25
I remember studying the clotting mechanism in A&P and it seeming like nothing more than a bunch of vague steps to memorize- it was obvious that there was so much more to the process and that the chemistry behind it would explain and make sense of these steps. Your description of the protein thrombin was clear and very readable. It finally made sense of what is happening in that process and the steps that we once had to memorize without full understanding of the "why".
ReplyDeleteI agree. I found it even more interesting when the blood clotting mechanism topic came up in class again the other day.
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