HEPARIN-SELENOCYSTAMINE CONJUGATE WITH SELENOL GROUPS

Heparin-selenocystamine conjugate, which was intended to mimic the hep arin-selenoprotein P complex, was prepared. The conjugate had glutathi one peroxidase-like activity and activity was observed toward hydrogen peroxide, tert-butyl hydroperoxide, and cumene hydroperoxide. The ult raviolet spectrum of an aqueous solution of the conjugate was stable a nd had a similar shape to that observed transiently when selenocystami ne was reduced by sodium cyanoborohydride; this suggests that the dise lenide bond of selenocystamine introduced into heparin was cleaved dur ing conjugate preparation and the selenol group is preserved. The conj ugate reacted to the same degree as cysteine with 5,5'-dithiobis (2-ni trobenzoic acid) (DTNB) releasing thionitro-benzoic acid, which indica ted that the selenium in the conjugate is present as selenol. However, the reaction rate of the conjugate was stower than cysteine which may be due to partially restricted access of DTNB to the selenol group in the conjugate. This conjugate had 1,1-diphenyl-2-picryl-hydrazyl(DPPH) radical scavenging activity as well as superoxide anion scavenging ac tivity. These results indicate that the conjugate serves as a useful m odel compound with a stable selenol group having a range of biological activities, and suggest a possible antioxidant defensive role for the complex of endogenous heparin-like substance and selenoprotein P.