Final answer:
Thrombin is the enzyme that converts soluble fibrinogen to insoluble fibrin during blood coagulation.
Step-by-step explanation:
The enzyme that converts soluble fibrinogen to insoluble fibrin is thrombin. After factor X is activated via the intrinsic or extrinsic pathway in the coagulation process, prothrombinase converts the inactive enzyme prothrombin (factor II) into the active enzyme thrombin. Thrombin then acts on fibrinogen (factor I), turning it into insoluble fibrin strands. These fibrin strands form a meshwork that traps blood cells and platelets, creating a clot that seals off the vessel. Finally, factor XIII stabilizes the fibrin clot, ensuring its durability while the vessel heals.
Interestingly, the body has mechanisms for clot removal once healing is underway, involving a process called fibrinolysis. During fibrinolysis, plasminogen is activated into plasmin, a protein that breaks down fibrin, thus gradually degrading the clot.