Question

Which one of the following amino acids is involved in synthesis of hormone epinephrine in humans?

• A. Threonine
• B. Tryptophan
• C. Tyrosine
• D. Phenylalanine

Hint:

Remember the precursors for key neurotransmitters/hormones: \textbf{T}yrosine \(\rightarrow\) \textbf{D}opamine, \textbf{N}orepinephrine, \textbf{E}pinephrine (Adrenaline). \textbf{T}ryptophan \(\rightarrow\) \textbf{S}erotonin.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Epinephrine (also known as adrenaline) is a catecholamine hormone and neurotransmitter. Like many biologically active molecules, it is synthesized from a specific amino acid precursor.
Step 2: Detailed Explanation:
The biosynthetic pathway for catecholamines proceeds as follows:


The starting amino acid is Tyrosine.

Tyrosine is converted to L-DOPA by the enzyme tyrosine hydroxylase.

L-DOPA is then converted to Dopamine.

Dopamine is converted to Norepinephrine (noradrenaline).

Finally, Norepinephrine is converted to Epinephrine (adrenaline).

So, the entire pathway starts with Tyrosine. While Phenylalanine (D) can be converted to Tyrosine in the body by the enzyme phenylalanine hydroxylase, Tyrosine itself is the direct precursor that enters the catecholamine synthesis pathway. Tryptophan (B) is the precursor for serotonin and melatonin. Threonine is not a precursor for these hormones.
Step 3: Final Answer:
Tyrosine is the amino acid directly involved in the synthesis of epinephrine.