Question

Cells can also convert a-keto acids into amino acids, but because the reagents organic chemists use for this reaction are not available in cells, they carry out this reaction by a different mechanism

(a) What amino acid is obtained from the reductive amination of each of the following metabolic intermediates in a cell by reductive amination?

(b) What amino acids are obtained from the same metabolic intermediates when the amino acids are synthesized in the laboratory?

Short answer

Answer:

(a)

(b)

Step-by-step solution

Synthesis of amino acids

When amino acids are synthesized in nature, only the l-enantiomer is formed. When amino acids are synthesized in the laboratory, however, the product is a racemic mixture of d- and l-amino acids. If only one isomer is desired, the enantiomers must be separated, which can be accomplished by an enzyme-catalyzed reaction.

Formation of the desired product

$\mathrm{\alpha }$-keto acids are converted into amino acids by reductive amination.

Formation of amino acids

(a)

• By the reductive amination, pyruvic acid gives the amino acid L-alanine which is represented as follows:

Pyruvic acid L-alanine

Formation of L-alanine

• By the reductive amination, oxaloacetic acid gives the amino acid L-aspartate (aspartic acid) which is represented as follows:

Oxaloacetic acid L-Aspartate

Formation of L-Aspartate

• By reductive amination, $\mathrm{\alpha }$-ketoglutaric acid gives L-glutamic acid which is represented as follows:

$\mathrm{\alpha }$-ketoglutaric acid L-glutamic acid

Formation of L-glutamic acid

(b)

• The anion acids are obtained from the same metabolic intermediates when the amino acids are synthesized in the laboratory. L-alanine and D-alanine from pyruvic acid are obtained

Pyruvic acid L-alanine + D- alanine

Formation of L-alanine and D-alanine

• L-aspartate and D-aspartate acid are formed from oxaloacetic acid in the laboratory which is represented as follows:

oxaloacetic acid L-aspartate and D-aspartate acid

Formation of L-aspartate and D-aspartate acid

• L-glutamate and D-glutamate from $\mathrm{\alpha }$-ketoglutaric acid is formed in a laboratory which is represented as follows:

Formation of L-glutamate and D-glutamate