Chapter 26, Problem 26.46EP

(a)

Interpretation Introduction

Interpretation: To characterize oxaloacetate 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 26.46EP

Oxaloacetate can function as a product both in transamination reaction oxidative deamination reactions.

Explanation of Solution

Oxaloacetate is a keto acid. 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.

Oxaloacetate is a corresponding keto acid of aspartate. Both of them have the same carbon skeleton. Aspartate gives oxaloacetate product in both transamination and oxidative deamination reaction.

(b)

Interpretation Introduction

Interpretation: To characterize aspartate 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 26.46EP

Aspartate acts as a reactant in transamination reaction.

Explanation of Solution

In transamination 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 transamination reaction is an amino acid.

Aspartate is an $\text{α-amino}$ acid thus acts as a reactant in transamination reaction to give corresponding keto acid oxaloacetate.

(c)

Interpretation Introduction

Interpretation: To characterize glutamate aminotransferase 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 26.46EP

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

Explanation of Solution

Aminotransferases are enzymes used for transamination reaction. These catalyze the interchange of an amino group from an $\text{α-amino}$ acid with a keto group of an $\text{α-keto}$ acid. Aminotransferase enzyme involved in the transfer of an amino group of glutamate amino acid is named as glutamate aminotransferase. Transamination reaction of glutamate requires Glutamate aminotransferase enzyme.

(d)

Interpretation Introduction

Interpretation: To characterize ${\text{H}}_{\text{2}}\text{O}$ 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 26.46EP

Water is one of the reactants 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: