Abstract
Abstract Previous studies from our laboratory have resulted in the separation of two major forms of plasminogen from rabbit plasma. These two forms differ in their affinity characteristics for antifibrinolytic amino acids, metabolic survival times in the circulation, charge characteristics of the subforms resolved from each major form, and sialic acid content. In order to investigate the role of sialic acid in determining these distinct properties of the plasminogen forms, we have studied these same properties of the asialo rabbit plasminogen forms. We find that the charge differences between the two forms are essentially abolished upon removal of the sialic acid. The number of subforms resolved from each major form is decreased as an effect of removal of the sialic acid, but the remaining subforms possess greatly increased isoelectric points. Contrarily, the binding of each plasminogen to antifibrinolytic amino acids appears no different from normal. The metabolic survival times of the asialoplasminogen forms are not greatly different from each other but are significantly lower than normal, a phenomena also found for many other circulating proteins. These studies suggest that the charge differences between the two forms of rabbit plasminogen are incidental to their functional differences.
Highlights
Proteins-Each major form of rabbit plasminogen as well as the subforms studied were purified as described in an earlier report from this laboratory (2)
1.2 mg of normal rabbit plasminogen Form 2 were dissolved in 2 ml of a solution consisting of 0.1 M phosphate, 0.15 M NaCl, pH 8.0
Two major forms of plasminogen can be resolved based on their differential affinity for antifibrinolytic amino acids of the e-aminocaproic acid class (1)
Summary
Previous studies from our laboratory have resulted in the separation of two major forms of plasminogen from rabbit plasma These two forms differ in their affinity characteristics for antifibrinolytic amino acids, metabolic survival times in the circulation, charge characteristics of the subforms resolved from each major form, and sialic acid content. The metabolic survival times of the asialoplasminogen forms are not greatly different from each other but are significantly lower than normal, a phenomena found for many other circulating proteins These studies suggest that the charge differences between the two forms of rabbit plasminogen are incidental to their functional differences. Our approach to the problem was to determine whether the differential properties of each form of rabbit plasminogen were conserved upon removal of the sialic acid This manuscript is a result of these studies
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