Abnormal Plasminogen Maywood I

Abstract

SummaryMaywood I is a dysfunctional plasminogen. It is described in a patient (W. Y) with a reduced plasma functional activity and with a low normal antigen level. Plasminogen was isolated from the patients plasma by affinity chromatography with L-lysine-substituted Sepharose. The protein yield was 86 mg/1, which was 88% of the plasma Plg antigen level; the specific activity was 24.4 IU/mg protein compared to 28.5 IU/mg protein for the native molecule. The protein was the Glu-form determined by SDS-PAGE and by isoelectric focusing. Six major isoelectric forms were found with isoelectric points between pH's 6.40 and 5.45. Titration of the equimolar plasminogen.streptokinase complex with p-nitrophenyl-p-guanidinobenzoate gave 85% active-sites indicating a homogenous population of molecules; therefore, the propositus is a homozygote. Four different plasminogen activators: a) streptokinase, b) urokinase c) the plasmin-derived light (B) chain-streptokinase complex, and d) tissue plasminogen activator (with soluble fibrin/CNBr-fibrinogen fragments) generated little plasmin from the variant plasminogen (4.5 to 45 nM), 5% or less than that generated from normal plasminogen. At 45 nM plasminogen, the molar ratio of plasminogen : activator was 3.0 for streptokinase, 3.9 for urokinase, 7.1 for the light (B) chain-streptokinase complex, and 155 for tissue plasminogen activator. In the equimolar variant plasminogen.streptokinase complex, the active-site was slowly developed, to a maximum of 85% in 40 min; in the normal complex, 100% active-sites were developed in 15 min. The variant plasminogen forms two equimolar complexes with streptokinase (I and II), with different mobilities in PAGE, in about equal amounts. About 10% of complex I (abnormal), with a slower mobility than complex II (normal), converts to plasmin.streptokinase in 60 min, whereas about 40% of complex II converts to plasmin.streptokinase in 60 min. A kinetic defect was also found with this variant plasminogen. It showed substantially lowered kinetics of activation second-order rate constants with both streptokinase and urokinase, primarily due to lower catalytic rate constants, and with streptokinase, a higher Michaelis constant. Crossed-immunoelectrophoresis, and preparative isoelectric focusing isoelectric points did not show a charge mutation. Maywood I may be classified as a dysplasminogenemia with active center and kinetic defects, Type 1c.