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The intrinsic pathway of apoptosis (also known as the mitochondrial pathway, intracellular pathway, or intrinsic apoptosis), cell death initiated by changes in mitochondria. The intrinsic pathway of blood coagulation (also known as the contact activation pathway), a cascade of enzymatic reactions resulting in blood clotting.
This test is used to measure the contact activation pathway (intrinsic pathway) and the common pathway of clotting. [7] FXII is a zymogen , which means that it requires processing to attain its catalytic protease activity.
It activates factor XI and prekallikrein in vitro. FXII is activated to FXIIa by negatively charged surfaces such as glass, initiating the intrinsic pathway. [ 12 ] FXII also plays a role in diagnostic coagulation assays called activated partial thromboplastin times (aPTT).
The contact activation (intrinsic) pathway is initiated by activation of the contact activation system, and can be measured by the activated partial thromboplastin time (aPTT) test. [ 48 ] The tissue factor (extrinsic) pathway is initiated by release of tissue factor (a specific cellular lipoprotein), and can be measured by the prothrombin time ...
The apoptosome triggers the activation of caspases in the intrinsic pathway of apoptosis. [12] The wheel-shaped heptameric complex with sevenfold symmetry structure of the apoptosome was first revealed at 27 Å resolution by electron cryomicroscopy techniques and has a calculated mass of about 1 MDa (Acehan et al. 2002). [2]
HMWK is one of four proteins which interact to initiate the contact activation pathway (also called the intrinsic pathway) of coagulation: the other three are Factor XII, Factor XI and prekallikrein. HMWK is not enzymatically active, and functions only as a cofactor for the activation of kallikrein and factor XII.
Factor X is activated, by hydrolysis, into factor Xa by both factor IX with its cofactor, factor VIII in a complex known as intrinsic pathway; and factor VII with its cofactor, tissue factor in a complex known as extrinsic pathway. [6] It is therefore the first member of the final common pathway or thrombin pathway.
One such signaling event is the introduction of granzyme B, which can activate initiator caspases, into cells targeted for apoptosis by killer T cells. [25] [26] This extrinsic activation then triggers the hallmark caspase cascade characteristic of the apoptotic pathway, in which caspase-3 plays a dominant role. [10]