 Plasmin

Plasmin is a protease that cuts fibrin into soluble products, helping dismantle a blood clot. It is produced by proteolytic activation of plasminogen, an inactive precursor. Activation of an existing precursor can switch on an enzymatic process without waiting for new protein synthesis.^[ref]

This supplies a useful contrast within clot biology. Thrombin helps form the fibrin network; plasmin helps remove it. In a simplified experiment, a fibrin gel can therefore be formed first and its subsequent breakdown measured after adding active plasmin. The observable loss of the network is a consequence of peptide bond cleavage, linking a molecular reaction to a macroscopic change in material structure.