29] Human plasminogen

Abstract

Publisher Summary Human plasminogen is known to possess multiple isoelectric forms, which can be isolated by isoelectric-focusing techniques. Glu-plasminogen 1 possesses multiple forms of pI values of 6.2, 6.3, 6.4, and 6.6. Glu-plasminogen possesses two isoelectric forms with pI values of 6.4 and 6.6. On the other hand, Lys77-plasminogen 1 contains three major isoelectric forms of pI 6.7, 7.2, and 7.5; whereas LysrT-plasminogen 2 contains three major forms of pI values 7.5, 7.8, and 8.1. Assays of plasminogen first require its conversion to plasmin by common activators. The conversion of human plasminogen to human plasmin is accomplished as a result of cleavage of the Arg-Val­-sl peptide bond. The enzyme is then assayed based on its ability to hydrolyze a-N-tosyl-Larginine methyl ester (TAME), utilizing a recording pH-stat to titrate the amount of acid, a-N-tosyl-L-arginine, liberated with time. Assays that rely on the spectrophotometric determination of the plasmin-catalyzed release of p -nitroanilide from the substrate H-D-valyl-L-leucyl-L-lysine-pnitroanilide dihydrochloride and on the determination of the plasmin-catalyzed release of p-nitrophenolate from N-Cbz-L-lysine-p - nitrophenyl ester 3° have also been fruitfully employed. Other assay methods for plasmin are available, such as the casein, azocasein, and fibrin plate assay.