Chapter 15, Problem 15.115EP

(a)

Interpretation Introduction

Interpretation:

To indicate whether B vitamin niacin is involved as a cofactor in the processes of (1) transamination, (2) oxidative deamination, (3) urea cycle, (4) carbon skeleton degradation to CAC intermediates, or (5) carbon skeleton degradation to non-CAC intermediates.

Concept introduction:

Cofactors are non-protein organic compounds that are used along with the enzymes and help to carry forward the reaction. The coenzymes containing B-vitamin serve as temporary carriers of atoms or functional groups in the redox and group transfer reactions associated with the metabolism of ingested food in order to obtain energy from the food.

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.

A urea cycle is a cyclic biochemical pathway that involves the production of urea using ammonium ions and aspartate molecules as nitrogen sources. The reactants in the formation of carbamoyl phosphate are ammonium ion, water, and carbon dioxide. The desired product of the urea cycle is urea.

There are 20 standard amino acids. Each amino acid has a different carbon skeleton and has a different degradation pathway for its carbon skeleton.

Answer to Problem 15.115EP

B vitamin niacin is involved as a cofactor in the process of oxidative deamination and in carbon skeleton degradation to non-CAC intermediates.

Explanation of Solution

Coenzyme nicotinamide adenine dinucleotide $\left({\text{NAD}}^{\text{+}}\right)$ and nicotinamide adenine dinucleotide phosphate $\left({\text{NADP}}^{\text{+}}\right)$ contain the B vitamin niacin.

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.

The oxidative deamination reaction of glutamate amino acid is as follows:

Nicotinamide adenine dinucleotide $\left({\text{NAD}}^{\text{+}}\right)$ is also involved in the carbon skeleton degradation pathway to non-CAC intermediates. An overview of the B vitamin participations in the degradation pathways for the carbon skeletons of the 20 standard amino acids is as follows:

(b)

Interpretation Introduction

Interpretation:

To indicate whether B vitamin folate is involved as a cofactor in the processes of (1) transamination, (2) oxidative deamination, (3) urea cycle, (4) carbon skeleton degradation to CAC intermediates, or (5) carbon skeleton degradation to non-CAC intermediates.

Concept introduction:

Cofactors are non-protein organic compounds that are used along with the enzymes and help to carry forward the reaction. The coenzymes containing B-vitamin serve as temporary carriers of atoms or functional groups in the redox and group transfer reactions associated with the metabolism of ingested food in order to obtain energy from the food.

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.

A urea cycle is a cyclic biochemical pathway that involves the production of urea using ammonium ions and aspartate molecules as nitrogen sources. The reactants in the formation of carbamoyl phosphate are ammonium ion, water, and carbon dioxide. The desired product of the urea cycle is urea.

There are 20 standard amino acids. Each amino acid has a different carbon skeleton and has a different degradation pathway for its carbon skeleton.

Answer to Problem 15.115EP

B vitamin folate is involved as a cofactor in carbon skeleton degradation to non-CAC intermediates.

Explanation of Solution

Coenzyme tetrahydrofolate $\left(\text{THF}\right)$ contains the B vitamin folate. Tetrahydrofolate $\left(\text{THF}\right)$ is involved in the carbon skeleton degradation pathway to non-CAC intermediates. An overview of the B vitamin participations in the degradation pathways for the carbon skeletons of the 20 standard amino acids is as follows:

(c)

Interpretation Introduction

Interpretation:

To indicate whether B vitamin biotin is involved as a cofactor in the processes of (1) transamination, (2) oxidative deamination, (3) urea cycle, (4) carbon skeleton degradation to CAC intermediates, or (5) carbon skeleton degradation to non-CAC intermediates.

Concept introduction:

Cofactors are non-protein organic compounds that are used along with the enzymes and help to carry forward the reaction. The coenzymes containing B-vitamin serve as temporary carriers of atoms or functional groups in the redox and group transfer reactions associated with the metabolism of ingested food in order to obtain energy from the food.

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.

A urea cycle is a cyclic biochemical pathway that involves the production of urea using ammonium ions and aspartate molecules as nitrogen sources. The reactants in the formation of carbamoyl phosphate are ammonium ion, water, and carbon dioxide. The desired product of the urea cycle is urea.

There are 20 standard amino acids. Each amino acid has a different carbon skeleton and has a different degradation pathway for its carbon skeleton.

Answer to Problem 15.115EP

B vitamin biotin is involved as a cofactor in carbon skeleton degradation to CAC intermediates.

Explanation of Solution

Biotin is involved in the carbon skeleton degradation pathway to CAC intermediates. An overview of the B vitamin participations in the degradation pathways for the carbon skeletons of the 20 standard amino acids is as follows:

(d)

Interpretation Introduction

Interpretation:

To indicate whether B vitamin ${\text{vitamin B}}_{\text{6}}$ is involved as a cofactor in the processes of (1) transamination, (2) oxidative deamination, (3) urea cycle, (4) carbon skeleton degradation to CAC intermediates, or (5) carbon skeleton degradation to non-CAC intermediates.

Concept introduction:

Cofactors are non-protein organic compounds that are used along with the enzymes and help to carry forward the reaction. The coenzymes containing B-vitamin serve as temporary carriers of atoms or functional groups in the redox and group transfer reactions associated with the metabolism of ingested food in order to obtain energy from the food.

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.

A urea cycle is a cyclic biochemical pathway that involves the production of urea using ammonium ions and aspartate molecules as nitrogen sources. The reactants in the formation of carbamoyl phosphate are ammonium ion, water, and carbon dioxide. The desired product of the urea cycle is urea.

There are 20 standard amino acids. Each amino acid has a different carbon skeleton and has a different degradation pathway for its carbon skeleton.

Answer to Problem 15.115EP

${\text{Vitamin B}}_{\text{6}}$ is involved as a cofactor in transamination reaction, carbon skeleton degradation to CAC intermediates, and in carbon skeleton degradation to non-CAC intermediates.

Explanation of Solution

Coenzyme ${\text{pyridoxal-5}}^{\text{'}}\text{-phosphate}\left(\text{PLP}\right)$ contains the B vitamin ${\text{vitamin B}}_{\text{6}}$ in its structure.

Transamination reaction involves a simple transfer of amino groups but the overall reaction occurs in several steps and also requires ${\text{pyridoxal-5}}^{\text{'}}\text{-phosphate}\left(\text{PLP}\right)$. ${\text{pyridoxal-5}}^{\text{'}}\text{-phosphate}\left(\text{PLP}\right)$ is a coenzyme produced from pyridoxine (vitamin ${\text{B}}_{\text{6}}$). The first step of transamination reaction involves the transfer of the amino group to the coenzyme pyridoxine which then transferred to $\text{α-keto}$ acid.

Coenzyme ${\text{pyridoxal-5}}^{\text{'}}\text{-phosphate}\left(\text{PLP}\right)$ is also involved in the carbon skeleton degradation pathway to non-CAC and CAC intermediates.

An overview of the B vitamin participations in the degradation pathways for the carbon skeletons of the 20 standard amino acids is as follows: