Studies on plasminogen. II. A comparison of the esterolytic, caseinolytic, and fibrinolytic activities of bovine and human plasminogen.

Abstract

Preparations of bovine and human plasminogen which varied in purity and mode of preparation were activated and assayed for esterolytic, caseinolytic, and fibrinolytic activities. Variations in the ratio of attack of bovine plasmin on TAMe and casein were observed among the plasminogen preparations which represent different stages of purification. Two plasminogen products with different TAMe/casein ratios were separated from both bovine and human products with intermediate TAMe/casein ratios, by the use of phosphate buffer as a precipitant. Bovine plasminogen preparations extracted with acid, then subjected to alkali denaturation, were purified with respect to their caseinolytic activity, but the esterolytic activity remained the same or decreased, resulting in a decrease in the TAMe/casein ratio. Human plasminogen prepared from fraction III by this method showed as much as a fourfold decrease in the TAMe/casein ratio. The observed differences in activity of various plasminogen preparations towards the two substrates, TAMe and casein, may arise from the chemical treatment and manipulation that the proenzyme receives during purification. When the fibrinolytic activity was compared with the caseinolytic activity, a single straight-line relationship was obtained for both bovine and human plasminogen preparations. However, a similar relationship was not found between the fibrinolytic and esterolytic activities.