Resumen de Modification of an Enzymatic Glutathione Assay for Determination of Total Glutathione in Grapevine Tissues
Douglas O. Adams, Chandrika Liyanage
In the course of adapting an enzymatic method for the spectrophotometric determination of glutathione in grapevines, we found that certain tissues, especially the rachis, contained a powerful inhibitor of yeast glutathione reductase (EC 1.6.4.2) used for the assay. Further experimentation showed that the inhibitor could be removed from 5% perchloric acid extracts by adding polyvinylpolypyrrolidone (PVPP) after adjusting the pH of the extract to 3.5 with 2 N KOH. This modification allows the assay of glutathione in leaves, rachis, and berries. Recovery of glutathione from perchloric acid extracts treated with PVPP was shown to be nearly quantitative and values for glutathione in Thompson Seedless berries obtained using the assay were in the range previously reported for other varieties.
