Chapter 15, Problem 15.45EP

(a)

Interpretation Introduction

Interpretation: To characterize $\text{α-Ketoglutarate}$ as a possible reactant, product, or enzyme involved in transamination, oxidative deamination, or both transamination and oxidative deamination.

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 $\text{α-keto}$ acid. There occurs no net loss or gain of amino acid in transamination reaction.

A biochemical reaction in which an $\text{α-amino}$ acid is converted into $\text{α-keto}$ acid along with the release of an ammonium ion is known as oxidative deamination reaction. It occurs mainly in kidney and liver mitochondria.

A general oxidative deamination reaction is as follows:

$\text{α-amino acid}+{\text{NAD}}^{+}+{\text{H}}_{\text{2}}\text{O}\to \text{α-keto acid}+{\text{NH}}_4^{+}+\text{NADH}+{\text{H}}^{+}$

Answer to Problem 15.45EP

$\text{α-Ketoglutarate}$ is a product in both transamination and oxidative deamination reaction of glutamate.

Explanation of Solution

In both transamination and oxidative deamination reaction exchange of an amino group from an $\text{α-amino}$ acid with a keto group of $\text{α-keto}$ acid takes place. The new keto acid formed has a carbon skeleton similar to the carbon skeleton of the reacting amino acid.

$\text{α-Ketoglutarate}$ is a corresponding keto acid of glutamate. Both of them have the same carbon skeleton. Glutamate gives $\text{α-ketoglutarate}$ product in both transamination and oxidative deamination reaction.

(b)

Interpretation Introduction

Interpretation: To characterize glutamate as a possible reactant, product, or enzyme involved in transamination, oxidative deamination, or both transamination and oxidative deamination.

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 $\text{α-keto}$ acid. There occurs no net loss or gain of amino acid in transamination reaction.

A biochemical reaction in which an $\text{α-amino}$ acid is converted into $\text{α-keto}$ acid along with the release of an ammonium ion is known as oxidative deamination reaction. It occurs mainly in kidney and liver mitochondria.

A general oxidative deamination reaction is as follows:

$\text{α-amino acid}+{\text{NAD}}^{+}+{\text{H}}_{\text{2}}\text{O}\to \text{α-keto acid}+{\text{NH}}_4^{+}+\text{NADH}+{\text{H}}^{+}$

Answer to Problem 15.45EP

Glutamate acts as a reactant in both transamination and oxidative deamination reaction.

Explanation of Solution

In both transamination and oxidative deamination reaction exchange of an amino group from an $\text{α-amino}$ acid with a keto group of $\text{α-keto}$ acid takes place. The reactant in both transamination reaction and oxidative deamination reaction is an amino acid.

Glutamate is an amino acid thus acts as a reactant in both transamination and oxidative deamination reaction to give corresponding keto acid $\text{α-ketoglutarate}$.

(c)

Interpretation Introduction

Interpretation: To characterize glutamate dehydrogenase as a possible reactant, product, or enzyme involved in transamination, oxidative deamination, or both transamination and oxidative deamination.

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 $\text{α-keto}$ acid. There occurs no net loss or gain of amino acid in transamination reaction.

A biochemical reaction in which an $\text{α-amino}$ acid is converted into $\text{α-keto}$ acid along with the release of an ammonium ion is known as oxidative deamination reaction. It occurs mainly in kidney and liver mitochondria.

A general oxidative deamination reaction is as follows:

$\text{α-amino acid}+{\text{NAD}}^{+}+{\text{H}}_{\text{2}}\text{O}\to \text{α-keto acid}+{\text{NH}}_4^{+}+\text{NADH}+{\text{H}}^{+}$

Answer to Problem 15.45EP

Glutamate dehydrogenase is the enzyme involved in the oxidative deamination reaction of glutamate to give $\text{α-ketoglutarate}$.

Explanation of Solution

Oxidative deamination reaction of glutamate requires dehydrogenase enzyme. It is an oxidoreductase enzyme and works with either ${\text{NADP}}^{+}$ and ${\text{NAD}}^{+}$ coenzyme. It oxidizes glutamate by reducing the coenzyme used.

(d)

Interpretation Introduction

Interpretation: To characterize ${\text{NH}}_4^{+}$ as a possible reactant, product, or enzyme involved in transamination, oxidative deamination, or both transamination and oxidative deamination.

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 $\text{α-keto}$ acid. There occurs no net loss or gain of amino acid in transamination reaction.

A biochemical reaction in which an $\text{α-amino}$ acid is converted into $\text{α-keto}$ acid along with the release of an ammonium ion is known as oxidative deamination reaction. It occurs mainly in kidney and liver mitochondria.

A general oxidative deamination reaction is as follows:

$\text{α-amino acid}+{\text{NAD}}^{+}+{\text{H}}_{\text{2}}\text{O}\to \text{α-keto acid}+{\text{NH}}_4^{+}+\text{NADH}+{\text{H}}^{+}$

Answer to Problem 15.45EP

The ammonium ion is one of the products obtained in oxidative deamination reaction of glutamate.

Explanation of Solution

Glutamate is an $\text{α-amino}$ acid thus upon oxidative deamination gives corresponding keto acid, an ammonium ion, $\text{NADH}$ and ${\text{H}}^{+}$. The reaction is as follows:

The ammonium ion formed is toxic if build up in the body. Ammonium ion acts as the “nitrogen carrier” for further reactions.