Heparin prevents thrombin inhibition by alpha 2 macroglobulin

Affinity chromatography of thrombin on modified polystyrene resins

Insoluble polystyrenes substituted with sulphonate and L-arginyl methyl ester (PAOM) present substituents mimicking the reactive binding site of antithrombin III. These materials have a specific affinity for thrombin. The binding of the enzyme is reversible and the eluted thrombin remains active. Consequently, these resins can be used as stationary phases in affinity liquid chromatography in order to purify thrombin with a high biological activity. The influence of different characteristics of such polymers (substitution ratio, average particle size, affinity constant, synthesis conditions) on the purification performance is studied. Human prothrombin complex concentrate is activated and applied onto the gel. A purified human thrombin of high specific activity is separated with a high recovery of biological activity of the enzyme.

Glycosaminoglycans and the control of cell surface proteinase activity

It is postulated that the metabolically variable fine structure of pericellular heparan glycosaminoglycans affects the ability of these molecules to influence cell proliferation-associated proteinase-catalysed reactions occurring at cell surfaces. Evidence suggesting the possibility of a wide repertoire of glycosaminoglycan-mediated positive and negative effects on such reactions is reviewed. It is suggested that clinical administration of compounds related chemically to heparins might usefully modulate cell proliferation-associated proteinase activity.

Heparin and the progressive anti-thrombin activity of alpha 2-macroglobulin

Interactions between alpha 2-macroglobulin (alpha 2M) and thrombin have been studied by spectroscopic, isotopic and electrophoretic methods in presence or in absence of heparin. It is shown that thrombin binds to alpha 2M in a 1:1 ratio. Fluorescamin labelled heparin of Mr 7 000 interacts with thrombin to form a 2:1 molar complex. This complex does not bind to alpha 2M and is unable to achieve any proteolytic cleavage of this protein. In contrast the interaction of alpha 2M with chymotrypsin is not significantly affected by the mucopolysaccharide. Moreover, heparin is unable to react with alpha 2M bound thrombin.