Textbook Question
What alkyl halide is used in the acetamidomalonic ester synthesis to prepare
a. lysine?
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29. Amino Acids
Proteins and Amino Acids
4:44 minutesProblem 41
Textbook Question
Indicate the peptides produced from cleavage by the indicated reagent:
a. His-Lys-Leu-Val-Glu-Pro-Arg-Ala-Gly-Ala by trypsin
b. Leu-Gly-Ser-Met-Phe-Pro-Tyr-Gly-Val by chymotrypsin
Verified step by step guidance1
Step 1: Understand the cleavage specificity of the reagents. Trypsin cleaves peptide bonds on the carboxyl side of lysine (Lys, K) and arginine (Arg, R), except when followed by proline (Pro, P). Chymotrypsin cleaves peptide bonds on the carboxyl side of aromatic amino acids: phenylalanine (Phe, F), tyrosine (Tyr, Y), and tryptophan (Trp, W), except when followed by proline (Pro, P).
Step 2: For part (a), identify the positions of lysine (Lys, K) and arginine (Arg, R) in the sequence His-Lys-Leu-Val-Glu-Pro-Arg-Ala-Gly-Ala. These are the cleavage sites for trypsin, provided they are not followed by proline (Pro, P).
Step 3: For part (a), split the peptide at the identified cleavage sites. Ensure that the cleavage occurs on the carboxyl side of the lysine (Lys, K) and arginine (Arg, R) residues, and list the resulting peptide fragments.
Step 4: For part (b), identify the positions of phenylalanine (Phe, F), tyrosine (Tyr, Y), and tryptophan (Trp, W) in the sequence Leu-Gly-Ser-Met-Phe-Pro-Tyr-Gly-Val. These are the cleavage sites for chymotrypsin, provided they are not followed by proline (Pro, P).
Step 5: For part (b), split the peptide at the identified cleavage sites. Ensure that the cleavage occurs on the carboxyl side of the aromatic residues, and list the resulting peptide fragments.
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Video duration:
4mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Proteolytic Enzymes
Proteolytic enzymes, or proteases, are enzymes that catalyze the breakdown of proteins into smaller peptides or amino acids by cleaving the peptide bonds. Different proteases have specific cleavage sites based on the amino acid sequence of the substrate. Understanding the specificity of these enzymes is crucial for predicting the products of protein digestion.
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Trypsin Specificity
Trypsin is a serine protease that preferentially cleaves peptide bonds at the carboxyl side of lysine (Lys) and arginine (Arg) residues. This specificity is essential for determining the resulting peptide fragments when a protein is digested by trypsin. Recognizing the positions of these amino acids in a peptide sequence allows for accurate prediction of the cleavage products.
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Chymotrypsin Specificity
Chymotrypsin is another serine protease that cleaves peptide bonds preferentially at the carboxyl side of aromatic amino acids such as phenylalanine (Phe), tryptophan (Trp), and tyrosine (Tyr). This characteristic enables the identification of peptide fragments produced from proteins containing these residues. Understanding chymotrypsin's specificity is vital for analyzing peptide sequences and their cleavage patterns.
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