Quantitative enzymic assay of human plasminogen and plasmin with azocasein as substrate

Abstract 1. 1. The conditions for quantitative enzymic assays for human plasminogen and human plasmin are described. 2. 2. Plasminogen is assayed by prior conversion to activator with an excess of streptokinase; the activator is then allowed catalytically to convert bovine plasminogen to bovine plasmin. The bovine plasmin is finally measured by using azocasein substrate. 3. 3. The assay for plasminogen is linear over a 5-fold range of concentration and is sensitive to 5 μg of plasminogen. The range of the plasmin assay is considerably greater but is approximately ten times less sensitive for the detection of plasminogen after quantitative conversion to plasmin. 4. 4. A simple two-point assay of plasminogen or plasmin was found to have adequate precision for fractionation studies.