Chapter 26, Problem 26.32EP

(a)

Interpretation Introduction

Interpretation: To determine whether glutamate can be converted to $\text{α-ketoglutarate}$ via a transamination reaction or not.

Concept introduction: Transamination reaction is a biochemical reaction that involves the transfer of an amino group. In transamination reaction exchange of an amino group from an $\text{α-amino}$ acid with a keto group of an $\text{α-keto}$ acid. There occurs no net loss or gain of amino acid in transamination reaction.

During transamination reaction the new keto acid formed has carbon skeleton similar to the carbon skeleton of the reacting amino acid and the new amino acid formed has the carbon skeleton similar to the carbon skeleton of the reacting keto acid.

Answer to Problem 26.32EP

Yes, glutamate can be converted to $\text{α-ketoglutarate}$ by transamination.

Explanation of Solution

Glutamate is an amino acid and its structure is:

$\text{α-ketoglutarate}$ is keto acid and its structure is:

Both glutamate and $\text{α-ketoglutarate}$ are ${\text{C}}_{\text{5}}$ species and have the same carbon skeleton. They differ only in the functional group attached. Glutamate has an amino functional and $\text{α-ketoglutarate}$ has a carbonyl functional group. Thus by interchanging an amino group of glutamate with a keto group from $\text{α-ketoglutarate}$; glutamate can be converted to $\text{α-ketoglutarate}$ by transamination.

(b)

Interpretation Introduction

Interpretation: To determine whether $\text{α-ketoglutarate}$ can be converted to glutamate via a transamination reaction or not.

Concept introduction: Transamination reaction is a biochemical reaction that involves the transfer of an amino group. In transamination reaction exchange of an amino group from an $\text{α-amino}$ acid with a keto group of an $\text{α-keto}$ acid. There occurs no net loss or gain of amino acid in transamination reaction.

During transamination reaction the new keto acid formed has carbon skeleton similar to the carbon skeleton of the reacting amino acid and the new amino acid formed has the carbon skeleton similar to the carbon skeleton of the reacting keto acid.

Answer to Problem 26.32EP

Yes, $\text{α-ketoglutarate}$ can be converted to glutamate by transamination.

Explanation of Solution

$\text{α-ketoglutarate}$ is keto acid and its structure is:

Glutamate is an amino acid and its structure is:

Both glutamate and $\text{α-ketoglutarate}$ are ${\text{C}}_{\text{5}}$ species and have the same carbon skeleton. They differ only in the functional group attached. Glutamate has an amino functional and $\text{α-ketoglutarate}$ has a carbonyl functional group. Thus by interchanging a keto group of $\text{α-ketoglutarate}$ with an amino group from glutamate; $\text{α-ketoglutarate}$ can be converted to glutamate by transamination.

(c)

Interpretation Introduction

Interpretation: To determine whether glutamate can be converted to aspartate via a transamination reaction or not.

Concept introduction: Transamination reaction is a biochemical reaction that involves the transfer of an amino group. In transamination reaction exchange of an amino group from an $\text{α-amino}$ acid with a keto group of an $\text{α-keto}$ acid. There occurs no net loss or gain of amino acid in transamination reaction.

During transamination reaction the new keto acid formed has carbon skeleton similar to the carbon skeleton of the reacting amino acid and the new amino acid formed has the carbon skeleton similar to the carbon skeleton of the reacting keto acid.

Answer to Problem 26.32EP

No, glutamate cannot be converted to aspartate by transamination.

Explanation of Solution

Glutamate is an amino acid and its structure is:

Aspartate is an amino acid and its structure is:

Transamination reaction involves the exchange of an amino group from an $\text{α-amino}$ acid with a keto group of an $\text{α-keto}$ acid. But because both aspartate and glutamate are amino acids also they have different carbon skeleton (aspartate is a ${\text{C}}_{\text{4}}$ species and glutamate is a ${\text{C}}_{\text{5}}$ species) glutamate cannot be converted to aspartate by transamination. After conversion via transamination reaction, an amino acid is converted into keto acid and vice-versa.

(d)

Interpretation Introduction

Interpretation: To determine whether $\text{α-ketoglutarate}$ can be converted to oxaloacetate via a transamination reaction or not.

Concept introduction: Transamination reaction is a biochemical reaction that involves the transfer of an amino group. In transamination reaction exchange of an amino group from an $\text{α-amino}$ acid with a keto group of an $\text{α-keto}$ acid. There occurs no net loss or gain of amino acid in transamination reaction.

During transamination reaction the new keto acid formed has carbon skeleton similar to the carbon skeleton of the reacting amino acid and the new amino acid formed has the carbon skeleton similar to the carbon skeleton of the reacting keto acid.

Answer to Problem 26.32EP

No, $\text{α-ketoglutarate}$ cannot be converted to oxaloacetate by transamination.

Explanation of Solution

$\text{α-ketoglutarate}$ is keto acid and its structure is:

Oxaloacetate is a keto acid and its structure is:

Transamination reaction involves the exchange of an amino group from an $\text{α-amino}$ acid with a keto group of an $\text{α-keto}$ acid. But because both oxaloacetate and $\text{α-ketoglutarate}$ are keto acids also they have different carbon skeleton (oxaloacetate is a ${\text{C}}_{\text{4}}$ species and $\text{α-ketoglutarate}$ is a ${\text{C}}_{\text{5}}$ species) $\text{α-ketoglutarate}$ cannot be converted to oxaloacetate by transamination. After conversion via transamination reaction, an amino acid is converted into keto acid and vice-versa.