Effect of Individual Caseins on Plasminogen Activation by Bovine Urokinase-Type and Tissue-Type Plasminogen Activators

Abstract

The effect was examined of individual caseins on the rate of plasminogen activation by bovine urokinase-type and tissue-type plasminogen activators. All individual caseins (α-CN. β-CN, and κ-CN) enhanced the activity of both types of plasminogen activators. Optimal concentrations for α-CN and β-CN were 5 and 25 μg/ml, respectively. The enhancement of enzymatic activity declined when concentrations of α-CN and β-CN were higher. In contrast, increasing concentrations of κ-CN from 0 to 200 μg/ml resulted in corresponding increases in activity of both types of plasminogen activators. On a weight basis, α-CN was the most effective enhancer of plasminogen activator activity. Indirect evidence obtained with experiments utilizing α-CN immobilized on agarose suggested that the effect is related to extensive binding of plasminogen and both types of plasminogen activators to casein. © 1995, American Dairy Science Association. All rights reserved.