Describe the biosynthetic pathway that produces catecholamines such as norepinephrine and epinephrine from amino acid precursors and explain how the lack of available amino acids precursors would impact homeostasis regulated by catecholamines.

Tyrosine and phenylalanine are amino acids required for the synthesis of catecholamines

Explanation:

The catecholamines are hormones composed of a catechol ring group (benzene) and an amine lateral chain. One of the most common catecholamines is the neurotransmitter norepinephrine (noradrenaline). The biosynthesis pathway of the norepinephrine hormone includes the following steps: 1-tyrosine hydroxylase produces L-DOPA from tyrosine, 2-L-DOPA is subsequently tranformed into dopamine by the L-amino acid decarboxylase, and finally, 3-this chemical precursor is converted into norepinephrine by the action of the dopamine β-hydroxylase.  

Phenylketonuria is a congenital metabolic disease associated with a decrease in the metabolism of phenylalanine (Phe), which is an amino acid residue that acts as a precursor of different catecholamines including dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline). Dietary restriction of tyrosine and phenylalanine is the most common treatment against phenylketonuria.