Cleavage of laminin by thrombin and plasmin: Alpha thrombin selectively cleaves the beta chain of laminin

Highly purified -thrombin, plasmin and urokinase were incubated with laminin, type IV collagen and type V collagen. At 25°C (1:100 enzyme to substrate ratio on a weight/weight basis) -thrombin selectively degraded the β chain of native laminin, whereas plasmin degraded both the and β chains. The specific limited cleavage fragments of laminin produced by -thrombin and plasmin retained the ability to mediate binding of epithelial cells to type IV collagen. These serine proteases failed to degrade native type IV or type V collagen under identical experimental conditions. At 35°C type V collagen, but not type IV collagen, was partially cleaved by both -thrombin and plasmin. Urokinase failed to degrade any of the substrates. It is concluded that thrombin and plasmin could play a physiological role in the degradation of laminin during tissue remodeling or repair. Specific laminin cleavage products produced by these enzymes could be useful in structural, immunological, and biological studies.