DISULFIDE-DISULFIDE INTERCHANGE CATALYZED BY A LIVER SUPERNATANT ENZYME

An enzyme widely distributed in rabbit tissues which catalyzes an interchange between N,N-di-dinitrophenyl-l-cystine and oxidized glutathione to form the mixed disulfide is described. d-Penicillamine disulfide can be substituted for oxidized glutathione and the mixed disulfide of cysteine and glutathione can serve as the sole substrate giving as one product of interchange, oxidized glutathione. The enzyme is very labile and only limited purification of it has been achieved. The activity increases with increasing pH above 6.6, the Km for N,N-di-dinitrophenyl-l-cystine is 0.2 mM and for oxidized glutathione 0.8 mM. The enzyme is inhibited by SH reagents with protection against iodoacetamide inactivation provided by N,N-di-dinitrophenyl-l-cystine. Evidence is presented that disulfide-disulfide interchange enzyme is a different activity from the previously described protein disulfide isomerase and thiol transferase. © 1979.