Which enzyme is responsible for converting fibrinogen to fibrin during coagulation?

Thrombin is the enzyme that plays a crucial role in the coagulation cascade by converting fibrinogen into fibrin. This conversion is a key step in the formation of a blood clot, as fibrin strands weave through platelets to stabilize the clot. Thrombin is produced from prothrombin in response to tissue injury and plays a pivotal role in the final stages of hemostasis. Furthermore, thrombin not only converts fibrinogen to fibrin but also has additional functions, including activating platelets and promoting further coagulation processes.

Other options, while relevant to coagulation processes, do not perform the specific conversion of fibrinogen to fibrin. Fibrinogen is the substrate that thrombin acts upon but does not have a role as an enzyme. Prothrombin is the precursor to thrombin but does not directly convert fibrinogen to fibrin. Vitamin K is essential for the synthesis of certain clotting factors but does not perform the enzymatic activity involved in fibrin formation itself. Thus, the correct role of thrombin as the enzyme responsible for this conversion clarifies its crucial position in the coagulation process.