Chemical properties of the amino acids - Lecture 3

Question 1

A) Reactions of the amino acids due to carboxyl group, examples:

Answer 1

A1) Decarboxylation reaction

A2) Reaction with ammonia

A3) Estherificyation reaction

A4) Reaction with LiBH₄

Question 2

A1) Decarboxylation reaction:

Answer 2

The amino acid is transformed into the corresponding amine with releasing of CO₂

Biologically important amines produced in the body from amino acids:

Histidine -> Histamine + CO₂

Tyrosine -> Tyramine + CO₂

Tryptophan -> Tryptamine + CO₂

Glutamic acid -> Gamma - aminobutyric acid (GABA) + CO₂

Question 3

A2) Reaction with ammonia (NH₃)

Answer 3

→The COOH group from the radical of monoamino dicarboxylic amino acid can combine with ammonia to form the corresponding amide

Glutamic acid + NH₃ → Glutamine + H₂O

Aspartic acid + NH₃ → Asparagine + H₂O

Question 4

A3) Estherification reaction

Answer 4

The carboxylgroup of the amino acid combine with alcohol to form esther with releasing of water.

important to protect the carboxyl group in peptide synthesis.

Question 5

A4) Reaction with LiBH₄

Answer 5

the reaction is used for determination of the sequence of amino acids in proteins

Question 6

B) Reactions of the amino acids due to the amino group

Answer 6

B1) Transamination reaction

B2) Oxidative deamination reaction

Question 7

B1) Transamination reaction

Answer 7

The amino group of an amino acid is transfered to a keto acid forming a new amino acid an another keto acid by transaminase

Question 8

The two most important transaminases (or aminotransferases) in our body are:

Answer 8

GOT (glutamtate oxaloacetate transaminase)

or

AST (asparte aminotransferase)

GPT (glutamate pyruvate transaminase)

or

ALT (alanine aminotransferase)

Question 9

The serum activity of GOT increases in:

Answer 9

• acute hepatitis
• liver necrosis
• myocardial infarction

Question 10

The serum activity of GPT increases in:

Answer 10

• acute haptitis
• liver necorsis

Question 11

B2) Oxidative deamination reaction

Answer 11

The amino group of an amino acid is removed as free amonia (NH3) and the amino acid is transformed into the coresponding keto acid.

The major oxidative deamination reaction is given by glutamic acid. The reaction is catalyzed by glutamate dehydogenase, an enzyme which use NAD+ or NADP+ as coenzyme.

Question 12

B3) Reaction with fluorodinitrobenzene (FDNB) (Sanger reagent)

Answer 12

This reaction is used to determine the N-terminal amino acid pf a polypeptide.