Which bond does urokinase cleave to convert plasminogen into plasmin?

Urokinase is a serine protease that plays a critical role in the fibrinolytic system by converting plasminogen into plasmin, which is essential for the breakdown of fibrin in blood clots. The key reaction involves the cleavage of a specific bond within the plasminogen molecule.

The conversion primarily involves the Arg-Val bond, which is a part of the molecular structure of plasminogen. By cleaving this bond, urokinase activates plasminogen, leading to its transformation into plasmin, the active enzyme that digests fibrin and dissolves blood clots. This action is pivotal in regulating clot formation and resolving thrombosis.

The other options, which involve different amino acid bonds, do not correspond to the specific cleaving action performed by urokinase on plasminogen and, therefore, do not facilitate the conversion of plasminogen into plasmin. Thus, the correct understanding revolves around the identification of the Arg-Val bond as the target for urokinase's enzymatic activity.