In the tripeptide glutathione (γ-glutamyl-cysteinyl-glycine), the side chain carboxyl group of glutamate forms a peptide bond with the α-amino group of cysteine.The α-amino and α-carboxyl groups of glutamate do not participate in peptide bonds.Approximately what is the isoelectric point (pK) of glutathione?

Question

Quizplus · Accepted Answer

There is an α-amino group (of glutamate) with a pK near 9 or 10, an α-carboxyl group (of glutamate) with a pK near 2, a carboxyl terminus (formed by glycine) with a pK near 4, and a cysteine sulfhydryl group (SH) with a pK near 8.The isoelectric point is halfway between the pK values of the two carboxyl groups.

In the Tripeptide Glutathione (γ-Glutamyl-Cysteinyl-Glycine), the Side Chain Carboxyl Group