Effect of oversulfation on the chemical and biological properties of chondroitin-4-sulfate.

Chondroitin-4-sulfate was oversulfated using chlorosulfonic acid-pyridine complex and was isolated as the sodium salt. A comparison of the infrared analysis of the native (N-2) and oversulfated (S-2) compounds showed that the two spectra were identical except for a new peak in S-2 at 825 cm corresponding to the equatorial C-6 position of galactosamine. There was a 2.7-fold increase of sulfate content in S-2 and a generation of a significant anticoagulant activity as measured by doubling of the prothrombin time of normal citrated human plasma using 7.5 microg, while N-2 was inactive even at 2,000 microg. The result of the in-vitro studies of the activation of glutamic plasminogen by tissue plasminogen activator (t-PA) or by high-molecular-weight urokinase using 0.05 mol/l Tris buffer (pH 7.35) containing a physiological concentration of NaCl (0.9%) showed that 28.6 microg/ml S-2 enhanced the activation by three-fold to four-fold by t-PA or by urokinase, while the same concentrations of N-2 or unfractionated heparin gave less than 30% enhancement of t-PA and no enhancement of urokinase. The mechanism of enhancement by S-2 was investigated by dilution studies. The results showed that S-2 interacted with both urokinase or t-PA and glutamic plasminogen favoring a template model, while N-2 or unfractionated heparin interacted only with t-PA.