title: Reversible modification of thiol-containing polypeptides with poly (ethylene glycol) through formation of mixed disulfide bonds. The case of papaya proteinase III.
abstract: Papaya proteinase III (PPIII) was purified, as the S-methylthio derivative from the latex of Carica papaya L., by ion-exchange chromatography. Separation of reactivable PPIII from the irreversibly oxidized molecular species of this enzyme was readily achieved after a selective conversion of the reactivated proteinase into the S-monomethoxypoly(ethylene glycol)thio derivative (S-mPEG thio PPIII). From this derivative, a PPIII preparation titrating 1 mol of thiol/mol of enzyme was regenerated. From the physicochemical properties of S-mPEG thio PPIII that were investigated, it is concluded that interactions between the mPEG and the PPIII chains occur only to a limited extent. In addition to its usefulness for purifying thiol-containing enzymes, the mPEG modification resulting from mixed disulfide bond formation may find other practical applications.
authors.affiliation: Faculté de Médecine, Université Libre de Bruxelles, Bruxelles, Belgium.
authors.forename: T
authors.initials: T
authors.lastname: Musu
authors.forename: M
authors.initials: M
authors.lastname: Azarkan
authors.forename: J
authors.initials: J
authors.lastname: Brygier
authors.forename: C
authors.initials: C
authors.lastname: Paul
authors.forename: J
authors.initials: J
authors.lastname: Vincentelli
authors.forename: D
authors.initials: D
authors.lastname: Baeyens-Volant
authors.forename: C
authors.initials: C
authors.lastname: Guermant
authors.forename: M
authors.initials: M
authors.lastname: Nijs
authors.forename: Y
authors.initials: Y
authors.lastname: Looze
mesh_terms: D002942:Circular Dichroism; D003546:Cysteine Endopeptidases / Q000737:chemistry*; D004220:Disulfides; D010944:Plants / Q000201:enzymology*; D011092:Polyethylene Glycols
chemical_list: D004220:Disulfides; D011092:Polyethylene Glycols; D003546:Cysteine Endopeptidases