Problem 92 - Chemistry The Central Science

Question

Glutathione is a tripeptide found in most living cells. Partial hydrolysis yields Cys-Gly and Glu-Cys. What structures are possible for glutathione?

Step-by-Step Solution

Answer

The only possible structure of glutathione, based on the given hydrolysis products, is Glu-Cys-Gly. This is because the hydrolysis products, Cys-Gly and Glu-Cys, imply that there is a peptide bond between Cys and Gly and another peptide bond between Glu and Cys.

Step 1: Identify the amino acids involved

Glutathione is a tripeptide, which means it is composed of three amino acids. From the given information, we see that the hydrolysis products are Cys-Gly and Glu-Cys, so we can determine that the three amino acids involved are Cysteine (Cys), Glycine (Gly), and Glutamic acid (Glu).

Step 2: Analyze the hydrolysis products

In order to determine the original structure of glutathione, it is crucial to analyze the products formed after partial hydrolysis. The two products are Cys-Gly and Glu-Cys. This tells us that Cys is connected to Gly and Glu is connected to Cys in the original structure.

Step 3: Determine the possible structures of glutathione

To find the possible structures of glutathione, we will look at how these three amino acids can be connected. Based on the hydrolysis products, there are two possible ways in which these amino acids can be connected: 1. Glutathione structure 1: Glu-Cys-Gly 2. Glutathione structure 2: Gly-Glu-Cys However, we need to recognize that glutathione has a specific structure and not all possible arrangements are feasible. The hydrolysis products give us essential information about the connectivity between amino acids. The hydrolysis product Cys-Gly implies a peptide bond between Cys and Gly; similarly, the product Glu-Cys implies a peptide bond between Glu and Cys. Based on this information, the only possible structure of glutathione is Glu-Cys-Gly.