Inhibition of Heparinase Depolymerization of Unfractionated Heparin by Sulfaminoheparosans

Sulfaminoheparosans (SAHs) are biotechnologically derived heparin analogs composed of sulfated glucuronic acid/iduronic acid and glucosamine. Though structurally and functionally similar to heparin (UFH), SAHs are resistant to digestion by heparinase‐I. To test the hypothesis that SAHs inhibit heparinase‐I, studies were undertaken to determine the effect of two derivatives of SAH with MWs of 6 kDa (Bio‐6) and 20 kDa (Bio‐20), respectively on the depolymerization of heparin using a defined system containing UFH (10 mg/ml), 0.1 M CaCl 2 , graded amounts of Bio‐6 and Bio‐20 (5.0 – 0.62 mg/ml) and heparinase‐I (0.1 U/ml). Heparinase‐I digested both UFH and enoxaparin into lower MW oligosaccharides (MW= 3–5 kDa). Both Bio‐6 and Bio‐20 concentration dependently inhibited heparinase‐I resulting in the decreased generation of the lower MW oligosaccharides. Inhibition of the depolymerization of heparin was stronger than that of enoxaparin. On a gravimetric basis, Bio‐20 was a stronger inhibitor than Bio‐6. Functional studies using the activated clotting time in whole blood and the activated partial thromboplastin time (APTT) in citrated plasma confirmed these observations. Similar results were obtained with other LMWHs such as dalteparin, tinzaparin and fraxiparin. These results suggest that SAH derivatives are capable of inhibiting heparin digesting enzymes such as heparinase‐I and that additional studies are warranted to investigate the modulatory actions of SAHs on other heparin digesting enzymes such as heparinase‐II, heparinase‐III and heparanases