J. Leon et al., Reduction of Cys(36)-Cys(42) and Cys(64)-Cys(74) disulfide bonds in recombinant human granulocyte colony stimulating factor, J PHARM B, 19(6), 1999, pp. 837-845
The Cys(36)-Cys(42) and Cys(64)-Cys(74) disulfide bonds in recombinant meth
ionyl human granulocyte colony-stimulating factor were reduced to sulfhydry
ls with dithiothreitol or mercury. Both reduction reactions are dependent o
n the pH. The reduction reaction with dithiothreitol increased in rate with
increasing pH; between pH 7-9 and above pH 10.5 this increase was less tha
n in other regions. These observations are explained by repulsive forces be
tween dithiothreitol and regions in granulocyte colony-stimulating factor w
hich intensify in these pH-regions. The hydroxyl catalysis causes the overa
ll increase in k(obs) in the pH-region studied. The reduction of the disulf
ides with mercury is, as could be expected from the Nernst equation for dis
ulfide reduction, also pH dependent: the half-wave potential decreases with
increasing pH as predicted by theory. (C) 1999 Elsevier Science B.V. All r
ights reserved.