Structure-activity relationships of heparin. Independence of heparin charge density and antithrombin-binding domains in thrombin inhibition by antithrombin and heparin cofactor II.

Abstract

A B S T R A C T To better understand how heparin structure affects its activity the relationships between the functional domains for inhibitor binding and charge density were investigated to determine how these domains affect heparin-mediated thrombin inhibition by two different heparin-dependent protease inhibitors, antithrombin (AT) and heparin cofactor II (HC II). A series of heparins, fractionated systematically by charge density, was further fractionated on antithrombin agarose to isolate more homogeneous subfractions that were either inactive or highly active with respect to thrombin inhibition by AT. With AT, the activities of the AT-active subfractions increased sharply with heparin charge density, while those with little or no affinity for AT were virtually inactive. In contrast, with HC II inhibitor, the activities of the heparins depended only upon their charge densities and were independent of AT affinity. At any given charge density, the heparin before fractionation by AT affinity and the fractions that were highly active and inactive with AT were all equally active with HC II. The two inhibitors also differed in their reactivity with heparan sulfate and dermatan sulfate. A charge-density effect with the subfractions having similar high affinity for AT demonstrates that charge density rep-

A heparin binding synthetic peptide from human HIP / RPL29 fails to specifically differentiate between anticoagulantly active and inactive species of heparin

“…Secondly, HIP peptide-1 binds some ATIII depleted Hp byproducts indicating that the ATIII binding pentasaccharide is not essential for HIP peptide-1 binding. The inherently high negative charge of ATIII binding species [11,12] and the charge heterogeneity of Hp byproducts makes the HIP peptide-1 separation of Hp byproducts into pools with low and high anticoagulant activity possible. In contrast, the relatively homogeneously charged Hp preparations tested are refractory to a similar separation.…”

Heparin Is a Major Activator of the Anticoagulant Serpin, Protein Z-dependent Protease Inhibitor

“…3, A and C). These modest differences are probably due to the higher sulfation of the pentasaccharide-containing chains than chains lacking this sequence (26), a reflection of the greater extent of processing of the pentasaccharide-containing chains along the biosynthetic pathway (27). That the pentasaccharide sequence itself was not important for heparin rate enhancement was suggested by the observations that (i) the pentasaccharide alone showed no ability to accelerate the ZPI-factor Xa reaction rate (Fig.…”

Structure, function, and pathology of proteoglycans and glycosaminoglycans in the urinary tract

“…At a structural level we identified 17 different saccharide components in heparin using gas chromatography/mass spectrometry [1]. At a functional level a pentasaccharide sequence containing an unusual 3-sulfated 2-deoxy-2-sulfaminoglucose (synonomous with sulfaminoglucosamine) is necessary for high activity in enhancing the thrombin-antithrombin reaction of heparin [50], and even small differences in the charge density of heparins results in large differences in activity [19]. Recently, as the role of cell-surface heparan sulfates in the regulation of cell growth and binding of growth factors has begun to be understood, structural motifs necessary for biological activity have been implicated in these molecules as well [51].…”

“…The strength of the interaction between heparin and thrombin is directly related to heparin charge density and governs the enhancement of the thrombin-antithrombin reaction rate by heparin [5,19,36]. Model studies of the interactions of glycosaminoglycans with organic cations show that the high charge of the glycosaminoglycan produces an ordering of water molecules [31].…”