Question

Write the structure of the product formed by the Edman degradation of polypeptide Leu-Gly-Ala-Phe-Tyr-Val. What fragment of peptide chain will leave after the degradation reaction?

Short answer

The product is PTH-Leucine, and the remaining peptide chain is Gly-Ala-Phe-Tyr-Val.

Step-by-step solution

Understanding Edman Degradation

Edman degradation is a method used to sequence amino acids in a peptide. It sequentially removes one amino acid at a time from the N-terminal of a polypeptide.

Identify the N-terminal Amino Acid

Determine the first amino acid at the N-terminal of the polypeptide Leu-Gly-Ala-Phe-Tyr-Val. The sequence indicates that Leucine (Leu) is at the N-terminal position.

Reaction Mechanism of Edman Degradation

Edman degradation converts the N-terminal amino acid into a phenylthiohydantoin (PTH) derivative, which can be identified to determine the amino acid.

Removal of N-terminal Amino Acid

The PTH derivative of Leucine is cleaved from the polypeptide, effectively removing Leucine from the rest of the chain.

Identifying the Remaining Peptide Chain

After the removal of the PTH-Leucine, the remaining peptide chain is Gly-Ala-Phe-Tyr-Val.

Key concepts

Amino Acid Sequencing

Amino acid sequencing is the process of determining the order of amino acids in a polypeptide or protein. This is a fundamental technique in biochemistry for understanding protein structure and function. By knowing the sequence, scientists can infer the protein's properties and its biological role.

In the context of Edman degradation, amino acid sequencing involves sequentially removing and identifying each N-terminal amino acid of the polypeptide. This method is particularly useful for analyzing shorter polypeptides, typically those with 50 or fewer amino acids. The ability to determine the precise sequence of amino acids provides valuable insights into genetic information and protein synthesis.

Polypeptide Analysis

Polypeptide analysis involves examining the various aspects of polypeptide structure, including the sequence of amino acids, the length of the chain, and the chemical properties that influence its function.

Edman degradation is one specialized method used in this analysis to carefully dissect a polypeptide into its constituent amino acids. This process is crucial for researchers trying to understand complex biological molecules like enzymes, hormones, and antibodies. Through polypeptide analysis, scientists can thus gain a deeper understanding of an organism's physiology and biochemistry.

N-terminal Amino Acid

The N-terminal amino acid is the very first amino acid in a polypeptide chain. It plays a significant role in various biochemical processes due to its position. Identifying the N-terminal amino acid is a vital step in amino acid sequencing, as it anchors the beginning of the polypeptide's structure.

During Edman degradation, focusing on the N-terminal allows for the sequential removal of amino acids. For the polypeptide Leu-Gly-Ala-Phe-Tyr-Val, Leucine acts as the N-terminal amino acid. Its identification is crucial as it dictates the sequence of the removal process by Edman degradation, setting off the chain reaction to eventually identify the entire sequence.

Phenylthiohydantoin Derivative

The phenylthiohydantoin, or PTH, derivative is a crucial part of the Edman degradation process. When the N-terminal amino acid reacts with phenyl isothiocyanate during Edman degradation, it is converted into a PTH derivative.

This derivative is stable and can be easily identified through various analytical methods such as chromatography or mass spectrometry. The conversion of the N-terminal amino acid into a PTH derivative enables scientists to definitively identify the amino acid that was removed. This step-by-step identification is what makes Edman degradation such a reliable technique for determining amino acid sequences.