Ch.25 Protein and Amino Acid Metabolism

McMurry - Fundamentals of General, Organic, and Biological Chemistry 8th Edition

McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Not the one you use?Change textbook

McMurry 8th Edition

Ch.25 Protein and Amino Acid Metabolism

Problem 2

Chapter 25, Problem 2

Serotonin is a monoamine neurotransmitter. It is formed in the body from the amino acid tryptophan. What class of enzyme catalyzes each of the two steps that convert tryptophan to serotonin?

Verified step by step guidance

Step 1: Understand the biochemical pathway. The conversion of tryptophan to serotonin involves two enzymatic steps: (1) hydroxylation of tryptophan and (2) decarboxylation of the intermediate product.

Step 2: Identify the enzyme class for the first step. Hydroxylation involves the addition of a hydroxyl (-OH) group to the tryptophan molecule. Enzymes that catalyze hydroxylation reactions are typically classified as oxidoreductases, specifically monooxygenases or hydroxylases.

Step 3: Identify the enzyme class for the second step. Decarboxylation involves the removal of a carboxyl (-COOH) group from the intermediate product. Enzymes that catalyze decarboxylation reactions are classified as lyases, specifically decarboxylases.

Step 4: Relate the enzyme classes to the serotonin synthesis pathway. In the first step, tryptophan hydroxylase (an oxidoreductase) converts tryptophan to 5-hydroxytryptophan. In the second step, aromatic L-amino acid decarboxylase (a lyase) converts 5-hydroxytryptophan to serotonin.

Step 5: Summarize the enzyme classes. The first step is catalyzed by an oxidoreductase (hydroxylase), and the second step is catalyzed by a lyase (decarboxylase). These enzyme classes are essential for the biosynthesis of serotonin from tryptophan.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Serotonin and its Role

Serotonin is a crucial monoamine neurotransmitter that plays a significant role in regulating mood, sleep, and appetite. It is synthesized in the brain and intestines from the amino acid tryptophan, influencing various physiological functions and behaviors. Understanding serotonin's function is essential for grasping its importance in mental health and neurological disorders.

Tryptophan

Tryptophan is an essential amino acid that serves as a precursor for serotonin synthesis. It cannot be produced by the body and must be obtained through diet, found in foods like turkey, nuts, and dairy. The conversion of tryptophan to serotonin involves specific enzymatic reactions, highlighting its importance in neurotransmitter production.

Enzymatic Catalysis

Enzymatic catalysis refers to the process by which enzymes accelerate biochemical reactions. In the context of serotonin synthesis, two key enzymes are involved: tryptophan hydroxylase, which converts tryptophan to 5-hydroxytryptophan, and aromatic L-amino acid decarboxylase, which further converts 5-hydroxytryptophan to serotonin. Understanding these enzymes is crucial for comprehending the biochemical pathway of serotonin production.

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Related Practice

Textbook Question

What is the structure of the α-keto acid formed by transamination of the amino acid phenylalanine (Phe)?

Textbook Question

Unlike most amino acids, branched-chain amino acids are broken down in tissues other than the liver. Using Table 18.3, identify the three amino acids with branched-chain R groups. For any one of these amino acids, write the equation for its transamination.

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Textbook Question

Fumarate from step 3 of the urea cycle may be recycled into aspartate for use in step 2 of the cycle. The sequence of reactions for this process is

Classify each reaction as one of the following:

1. Oxidation

2. Reduction

3. Transamination

4. Elimination

5. Addition

Textbook Question

Decide whether each of the following statements is true or false. If false, explain why.

a. The amino acid pool is found mainly in the liver.