Question

Which of the following hormones is not involved in tyrosine metabolism?
A. Calcitonin
B. Melanin
C. Epinephrine
D. None of the above.

Answer 1

Hint: Tyrosine is a non-essential amino acid having a polar side group. UAC and UAU are the codons for tyrosine in messenger RNA. Synthesis of tyrosine in mammals is done from an essential amino acid, phenylalanine. Let us know more about it to find the correct answer.

Complete answer:
So tyrosine or L-Tyrosine (4-hydroxyphenylalanine) is one of the 20 standard amino acids used by cells for protein synthesis.
It is a non-essential amino acid synthesis from phenylalanine in mammals.
Tyrosine (tyr) is produced via prephenate ( a shikimate pathway intermediate) in plants and microorganisms.
Chicken, milk, yoghurt, fish, cheese, almonds, peanuts, lima beans , soy products,etc; are some of the high-protein food products in which tyrosine is found. It is also found in bananas and avocados.
Apart from being a proteinogenic amino acid, it has some other significant functions also.
It has its role in signal transduction processes. It occurs in proteins that are part of the signal transduction pathway, where it acts as a receiver of protein groups transferred by protein kinases.
An important role in photosynthesis is also played by tyrosine residue.
To talk of its metabolism, it is a precursor to many hormones, pigments, and alkaloids. Some to which tyrosine acts as precursor are-
Precursor to neurotransmitters and hormones such as epinephrine, norepinephrine, thyroxine.
Precursor to alkaloids such as alkaloid morphine.
Precursor to pigments such as melanin.
Calcitonin hormone is produced by parafollicular cells of the thyroid gland in humans. It helps to regulate calcium and phosphate levels in blood. It has antagonistic effects to that of parathyroid hormone. Tyrosine is not required as a precursor for its synthesis.

Thus based on the above discussion, the correct answer is (A)- Calcitonin.

Note:
Autosomal recessive disorders result from specific enzymes deficiencies in the tyrosine catabolic pathway. A number of studies suggest that tyrosine is useful in stress conditions, cold, sleep deprivation and prolonged work, with reductions in stress hormone levels.