Assays for Native Plasminogen Activators in Bovine Milk

Abstract

Assays for bovine milk plasminogen activators were developed. The colorimetric assay for bovine milk plasminogen activators was based on plasmin cleavage of the synthetic substrate Spectrozyme™. This substrate cleavage yielded the yellow chromophore p-nitroanilide, which was quantified spectrophotometrically at 405 nm with an ELISA plate reader. Correlation coefficients were >.995 for the linear regions of the standard curves for the assays. Modification of a previously reported casein-plasminogen SDS-PAGE system allowed visualization of plasminogen activators from bovine milk. This system can be used to determine the molecular mass of the milk plasminogen activators and to detect the activity of the plasminogen activators in a sample containing plasminogen activator inhibitors. © 1993, American Dairy Science Association. All rights reserved.