Molar extinction, glutathione

Glutathione-peroxidase activity was measured spectrophoto-metrically at 340nm by an enzyme coupled assay procedure of Paglia and Valentine (28) as modified by Reddy, et al. (26). A molar extinction coefficient of 6.2 x 103cm 1 was used in calculations. 

M. Calvin They re calculated from the graphs. Those graphs are not on the molar-extinction basis, so that we could have all the curves look about the same height, but the concentrations are given. I think that the molar extinctions for the thiazoline and for the glutathione are both between 6000 and 10,000. For the thiazoline I think it s near 10,000 for the glutathione it s about 6500. That, I think, is a pretty good correspondence. It would be pretty hard to have impurities. 

Fia. 4. Relation between the molar extinction coefficient of the nitroprusside color in water and its increase in 7 M urea for different thiols. Points from left to right are Thioglycolic acid, 8-mercapto-propionic acid (upper), homocysteine (lower) /3-mercaptoethanol (upper), cysteine (lower), coenzyme A, L-cysteinyl-n-valine, glutamyl-cysteine, L-oysteinyl-i.-valine, phenacetyl-cysteinyl-glycine, glutathione, phenacetyl-cysteinyl-D-valine. 

These results allow to correlate these absorbance changes with the presence of persulfide group in the enzyme molecule. The differential molar extinction coefficients for sulfur-free and sulfur-containing rhodanese were found to hezAs2j( = 550, As22 120 these values are very close to those obtained for persulfurated serum albumin and glutathione (see Table l). 

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