QUANTITATIVE-DETERMINATION OF BIOLOGICAL SULFHYDRYL-GROUPS BY POSTCOLUMN DERIVATIZATION AND ELUCIDATION OF MICROHETEROGENEITY OF SERUM ALBUMINS

A quantitative analytical system for biological sulfhydryl compounds h as been developed using an ion-pair reagent with isocratic elution and an on-line postcolumn derivatization with Ellman-type reagents. As hu man or bovine serum albumin has 35 cysteinyl residues, one cysteinyl r esidue exists as a free sulfhydryl moiety, and this gives rise to the microheterogeneity in serum albumin. Here we report for the first time the quantitative characterization of the microheterogeneity of serum albumin. Cysteine was found to be the major molecule attached to the s ulfydryl group of the serum albumins. Although glutathione could not b e detected, the Cys-Gly element of glutathione was found. Freshly prep ared human serum albumin from healthy volunteers contained 0.46 nmol o f Cys/mL of serum, 0.24 nmol of Cys-Gly/mL of serum, and very small am ounts of glutathione (0.02 nmol/ml).