Tyr is a precursor for neurotransmitter biosynthesis

Voet, Voet & Pratt. Biochemistry. 5th ed. (Dr. Purcell’s lecture)

Why is this important to us?

Dopamine

• It is a neurotransmitter that helps control the brains reward and pleasure centers. It also helps regulate movement and emotional responses. (https://www.psychologytoday.com/basics/dopamine)

Epinephrine

• It is involved in the human flight or fight response. The fight or flight response occurs when a person is subject to a threat. This causes a signalling process to occur, which causes the body to react to the potential danger. (http://www.news-medical.net/health/What-is-Epinephrine-(Adrenaline).aspx)

Norepinephrine

• It plays a central role in controlling alertness, rest cycles, attention and memory in the CNS. Like dopamine, it is a catecholamine and has structural similarity to methamphetamine. Its chemical formula is C₈H₁₁NO_{3 (https://www.macalester.edu/academics/psychology/whathap/ubnrp/meth08/biochemistry/norepinephrine.htm)}

*All three are synthesized by tyrosine*

 

Catabolic defects: lack of precursors for good stuff

• Tyrosine is not an essential amino acid EXCEPT in people with PKU
• Tyr is the precursor for biosynthesis of many neurotransmitters

– dopamine

–norepinephrine

–epinephrin

• Tyr is also a precursor for melanin biosynthesis

–PKU is associated with light hair and eyes

 

Retrieved from Dr. Purcell’s lecture

PAH- phenylalanine hydroxylase

human chromosome 12

>60 mutations that can lead to PKU

affects 1 in 10,000-25,000

• people heterozygous for functional PAH somewhat protected against fungal toxins

 

Wolf, LI. American Journal of Human Genetics. 1986. (Dr. Purcell’s lecture)

Amino acids are the building blocks of proteins

Retrieved from Voet, Voet & Pratt. Biochemistry. 5th ed. (Dr. Purcell’s lecture)

 

Individuals with PKU are missing the phenyalalanine hydroxylase enzyme. This enzyme is needed to break down phenylalanine (Phe=an essential AA).

Phe and Trp are essential, and must be obtained from diet. Tyr is synthesized from Phe.

 

Credit: Meletios /Shutterstock.com

 

Inborn errors of metabolism: Definition

Inborn errors of metabolism are rare genetic (inherited) disorders in which the body cannot properly turn food into energy. The disorders are usually caused by defects in specific proteins (enzymes) that help break down (metabolize) parts of food.

 

https://medlineplus.gov/ency/article/002438.htm