Reversible modification of thiol-containing polypeptides with poly (ethylene glycol) through formation of mixed disulfide bonds. The case of papaya proteinase III.
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.
Musu
T
T
Faculté de Médecine, Université Libre de Bruxelles, Bruxelles, Belgium.
Azarkan
M
M
Brygier
J
J
Paul
C
C
Vincentelli
J
J
Baeyens-Volant
D
D
Guermant
C
C
Nijs
M
M
Looze
Y
Y
D002942:Circular Dichroism; D003546:Cysteine Endopeptidases / Q000737:chemistry*; D004220:Disulfides; D010944:Plants / Q000201:enzymology*; D011092:Polyethylene Glycols
D004220:Disulfides; D011092:Polyethylene Glycols; D003546:Cysteine Endopeptidases