What are the amino acids degraded by Edman reaction?
Edman degradation is a method used to determine the sequence of amino acid residues from the N-terminus of a protein polypeptide chain, thereby identifying the primary structure of the protein. The essence of this method is the cyclic operation of chemical reactions for amino acid identification. The principle of Edman degradation includes three main chemical reactions: coupling of phenyl isothiocyanate (PITC) with the N-terminal residue of a protein or peptide, cyclization and cleavage of phenylthiocarbamoyl (PTC-peptide), and conversion of thiazolinone phenylamine (ATZ) to phenylthiohydantoin amino acid (PTH-amino acid). Each chemical reaction cycle cleaves one amino acid residue from the protein or peptide, exposing a new free amino acid for the next Edman degradation. The converted PTH-amino acids are then identified by HPLC to finally determine the N-terminal sequence of the protein.
According to the reaction principle of Edman degradation, it can be known that the amino acids degraded by the Edman reaction are the free α-amino acids at the N-terminus of the protein peptide chain, detaching them from the original peptide chain. These amino acids couple with the Edman reagent PITC in an alkaline environment to form the terminal residue's phenylthiocarbamoyl derivative (i.e., PTC-peptide). The coupling compound is then treated with acid to undergo subsequent chemical reactions and sequence determination.
In a polypeptide chain, amino acids are linked into a long chain through peptide bonds formed by the dehydration condensation of amino and carboxyl groups. The N-terminus of the peptide chain is the free α-amino group that has not formed a peptide bond. Therefore, the Edman reaction degrades the remaining peptide segment after cleaving one amino acid residue from each chemical cycle, with the degraded amino acid being the free α-residue at the N-terminus. The peptide segment is cyclically degraded, exposing new free α-amino acids for the next Edman degradation. The converted amino acids can be identified, and the amino acid sequence can be arranged from the C-terminus to the N-terminus to obtain the complete sequence of a pure protein or peptide chain.
Biotech Pack uses the Shimadzu Edman sequencing system to provideN-terminal sequencing of proteins based on Edman degradationservices for scientific researchers and clients. Using our sequencing system, the sequence information of 30 amino acids at the N-terminus can be determined. With a specific protein loading system, 60-70 amino acids at the N-terminus can be sequenced. Biotech Pack has also established a platform for N-terminal sequencing using advanced LC-MS/MS technology, capable of sequencing blocked and modified protein terminals, whichcomplements N-terminal protein sequencing based on Edman degradationto ensure the smooth progress of N-terminal sequencing services.
Related services:
Protein N/C-terminal sequencing
Biopharmaceutical N/C-terminal sequencing
Complete protein sequence determination
Protein sequencing based on the top-down approach
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