The reduction of serum albumin, insulin and some simple disulphides by glutathione

Abstract

The reduction of disulfide bonds in bovine serum albumin, insulin and a number of simple disulfides by physiological concentrations of glutathione was investigated. Glutathione reductase and reduced nicotine[long dash]adenine dinucleotide phosphate were used to follow the reactions spectrophotometrically. Serum albumin had approximately 0.5 of a rapidly reducible disulfide bond/molecule of protein. The remaining disulfide bonds of the native protein and also those of insulin were only slowly reduced by glutathione. On the hydrolysis of less than 10% of the peptide bonds of these proteins by chymotrypsin or trypsin or both there is a marked increase in the rate of reduction of the disulfide bonds. Reduction of simple disulfides with a nearby negative charge proceeds more slowly than that of other types. The factors concerned in the reduction of disulfide bonds of proteins by glutathione are discussed.