Which of the following chemical messengers) is/are derivatives) of
tryptophan?
Options:
(A) y-amino butyric acid
(B) Indole acetic acid
(C) | Melatonin
(D) Serotonin
Official Answer Key:
B,C,D
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2021 Q.47)**
**1. Governing Concept**:
- **Topic**: Biochemistry & Amino Acid Biosynthetic Derivatives
- **Tryptophan** is an essential aromatic amino acid that serves as the biosynthetic precursor for:
1. **Serotonin (5-hydroxytryptamine / 5-HT)**: Neurotransmitter synthesized via tryptophan hydroxylase and aromatic L-amino acid decarboxylase.
2. **Melatonin**: Pineal neurohormone synthesized by $N$-acetylation and $O$-methylation of serotonin.
3. **Indole-3-acetic acid (IAA)**: Primary plant auxin hormone synthesized from tryptophan via indole-3-pyruvate or tryptamine pathways.
4. **Nicotinamide (NAD$^+$/NADP$^+$)**: Via the kynurenine pathway in animals.
- In contrast, **Dopamine, Epinephrine, and Norepinephrine** (catecholamines) are synthesized from **Tyrosine**.
- **Histamine** is synthesized from **Histidine**.
- **GABA** is synthesized from **Glutamate**.
**2. Option Analysis**:
- **Option (A) [Dopamine] is INCORRECT**: Synthesized from tyrosine via L-DOPA.
- **Option (B) [Serotonin] is CORRECT**: Direct metabolic derivative of tryptophan via 5-HTP.
- **Option (C) [Melatonin] is CORRECT**: Synthesized directly from serotonin (and thus from tryptophan).
- **Option (D) [Indole-3-acetic acid (IAA)] is CORRECT**: Plant auxin synthesized from tryptophan.
**3. Final Answer**:
- **Correct Options**: **B, C, D**
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.