Problem 92 - Chemistry The Central Science In Si Units

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 structure of glutathione is Glu-Cys-Gly.

Step 1: Understand the Components

Glutathione is a tripeptide, which means it is composed of three amino acids. The partial hydrolysis products given are Cys-Gly and Glu-Cys. This implies that these two dipeptides can be formed from breaking the tripeptide at specific points.

Step 2: Identify Possible Structures

Given the dipeptides Cys-Gly and Glu-Cys, think of possible arrangements that would allow these dipeptides to exist after hydrolysis. The C-terminal of Glu-Cys must be Gly, while the C-terminal of Cys-Gly must be Glu. Consequently, the sequences must overlap.

Step 3: Visualize the Sequence

Consider the arrangement of these sequences. For Glutathione, the sequence must start and end with one of these sequences and have the third one in the middle. Glu-Cys followed by Gly could overlap to give Glu-Cys-Gly.

Step 4: Formulate the Linear Sequence

From the overlaps and the information from the dipeptides, we put Glu first (from Glu-Cys), followed by Cys, and then Gly (from Cys-Gly). Thus, the full sequence becomes Glu-Cys-Gly.

Key Concepts

Tripeptide Structure

In the fascinating world of biochemistry, a tripeptide is a molecule formed by three amino acids linked together. These amino acids are connected through peptide bonds, creating a distinct chain. A popular example of a tripeptide is glutathione, which plays various crucial roles in living cells. Each amino acid in a tripeptide is referred to as a residue, and they are named based on their sequence.

Here’s how you can understand tripeptide structures:

• The sequence is written from the amino (N) terminal to the carboxyl (C) terminal.
• Amino acids are connected in a linear fashion through peptide bonds.
• In glutathione, the sequence starts with glutamic acid (Glu), then cysteine (Cys), and ends with glycine (Gly).

The order of amino acids affects the properties and function of the tripeptide. Recognizing the sequence is essential for understanding its structure and potential interactions within cellular processes.

Peptide Bond Hydrolysis

Peptide bond hydrolysis is the process where peptide bonds in proteins or peptides are broken down with the addition of water. This is an important reaction that leads to the breakdown of proteins into smaller peptides or amino acids. For a tripeptide like glutathione, hydrolysis can provide insights into its structure.

Key points about peptide bond hydrolysis are:

• It involves the breaking of the bond between the carbon atom of one amino acid and the nitrogen atom of another.
• This reaction can happen naturally in the body, or it can be catalyzed by enzymes known as peptidases.
• The process results in smaller peptide chains or individual amino acids, which are useful for identifying the original structure.

When glutathione undergoes partial hydrolysis, it breaks down into dipeptides like Cys-Gly and Glu-Cys. Understanding these products can help reconstruct the tripeptide's original sequence.

Glutathione

Glutathione is a powerful tripeptide that serves as an antioxidant and is crucial for detoxification in cells. It is composed of three specific amino acids: glutamic acid (Glu), cysteine (Cys), and glycine (Gly). This unique combination allows it to play an essential role in maintaining cellular health.

Here’s what makes glutathione special:

• It protects cells from oxidative damage by neutralizing free radicals.
• It supports the immune system and aids in the regeneration of vitamins C and E.
• It helps detoxify harmful compounds such as pollutants and drugs within the liver.

The structure of glutathione, Glu-Cys-Gly, allows it to interact efficiently with oxidative molecules. Knowing the arrangement of its amino acids helps in understanding how it performs these vital functions and its roles in various biochemical pathways.