Question

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

Short answer

The possible structure of glutathione is Glu-Cys-Gly, with an alternative structure being Gly-Cys-Glu. However, it is important to note that Glu-Cys-Gly is the actual structure of glutathione based on the given partial hydrolysis products.

Step-by-step solution

Identify the amino acids in the products

After partial hydrolysis, we get two products: Cys-Gly and Glu-Cys. From these products, we can identify that the three amino acids involved in the formation of glutathione are: 1. Cysteine (Cys) 2. Glycine (Gly) 3. Glutamic acid (Glu) Now, we will find the possible structures of glutathione using these amino acids.

Order the amino acids in the sequence

We are given two partial hydrolysis products: Cys-Gly and Glu-Cys. The presence of these peptides suggests the linkage present in glutathione: 1. Cysteine (Cys) is connected to Glycine (Gly) 2. Glutamic acid (Glu) is connected to Cysteine (Cys) Therefore, the sequence of amino acids can be represented as Glu-Cys-Gly or, alternatively, Gly-Cys-Glu.

Determine the possible structures of glutathione

Considering the sequence of amino acids determined in Step 2, there are two possible structures for glutathione: 1. Glu-Cys-Gly - In this structure, Glutamic acid (Glu) is connected to Cysteine (Cys), which is further connected to Glycine (Gly). 2. Gly-Cys-Glu - In this structure, Glycine (Gly) is connected to Cysteine (Cys), which is further connected to Glutamic acid (Glu). It is essential to note that the linkage between amino acids in the peptides is through peptide bonds formed by the reaction of the carboxyl group of one amino acid and the amino group of another amino acid. Given that our available information is limited to the partial hydrolysis products, we cannot definitively determine the actual structure of glutathione. However, we do know Glu-Cys-Gly is glutathione due to the partial hydrolysis products given. The other structure, Gly-Cys-Glu, could be considered a possible alternative structure. In summary, the possible structure of glutathione is Glu-Cys-Gly, with an alternative structure Gly-Cys-Glu.