PHARMACOLOGICAL ADVANTAGES OF CONJUGATION OF CU,ZN-SUPEROXIDE DISMUTASE WITH SUCCINYLATED KERATIN FRAGMENT - IMPROVEMENT OF BIOLOGICAL PROPERTIES AND RESISTANCE TO OXIDATIVE DAMAGE

To improve the in vivo pharmacological potential of Cu,Zn-superoxide d ismutase (Cu,Zn-SOD), human recombinant Cu,Zn-SOD was conjugated with succinylated keratin fragment (Suc-ker). Suc-ker-conjugated Cu,Zn-SOD (Suc-ker-SOD) was formed by attachment of about 3.7 mol of Suc-ker to 1 mol of Cu,Zn-SOD and exhibited an apparent mean molecular weight of 107 kDa. Suc-ker-SOD exhibited 74.1% SOD activity on a molar basis. Wh en Suc-ker-SOD was administered i.v. into mice, its plasma half-life w as prolonged to 20.5 min compared with 4.7 min for native SOD. After i .v. administration of Cr-51-labeled proteins into mice, native SOD was excreted rapidly into urine and no significant accumulation was obser ved in organs other than the kidneys. On the other hand, Suc-ker-SOD w as taken up rapidly by the liver. Furthermore, Suc-ker-SOD exhibited m uch lower immunogenicity and much better therapeutic effects than nati ve and poly(styrene-co-maleic acid)-conjugated SOD against paraquat to xicity in mice. Moreover, the inactivation rate of Suc-ker-SOD by H2O2 was less than those of native SOD and polyethylene glycol-conjugated SOD. The effect of H2O2 on liganded Cu++ in the active site of Suc-ker -SOD was much less than those of other SOD derivatives. These results indicate that Suc-ker-SOD has advantages over the other SOD derivative s tested.