Physiology
Factor X is synthesized in the liver and requires vitamin K for its synthesis.
Factor X is activated into factor Xa by both factor IX (with its cofactor, factor VIII in a complex known as intrinsic Xase) and factor VII with its cofactor, tissue factor (a complex known as extrinsic Xase). It is therefore the first member of the final common pathway or thrombin pathway.
It acts by cleaving prothrombin in two places (an arg-thr and then an arg-ile bond), which yields the active thrombin. This process is optimized when factor Xa is complexed with activated co-factor V in the prothrombinase complex.
Factor Xa is inactivated by protein Z-dependent protease inhibitor (ZPI), a serine protease inhibitor (serpin). The affinity of this protein for factor Xa is increased 1000-fold by the presence of protein Z, while it does not require protein Z for inactivation of factor XI. Defects in protein Z lead to increased factor Xa activity and a propensity for thrombosis.
The half life of factor X is 40-45 hours.
Read more about this topic: Factor X
Famous quotes containing the word physiology:
“The world moves, but we seem to move with it. When I studied physiology before ... there were two hundred and eight bones in the body. Now there are two hundred and thirty- eight.”
—Ellen Henrietta Swallow Richards (1842–1911)
“A physician’s physiology has much the same relation to his power of healing as a cleric’s divinity has to his power of influencing conduct.”
—Samuel Butler (1835–1902)
“I have more in common with a Mexican man than with a white woman.... This opinion ... chagrins women who sincerely believe our female physiology unequivocally binds all women throughout the world, despite the compounded social prejudices that daily affect us all in different ways. Although women everywhere experience life differently from men everywhere, white women are members of a race that has proclaimed itself globally superior for hundreds of years.”
—Ana Castillo (b. 1953)