Synthesis Of Phenylalanine

Amino acids that are essential for humans are those that cannot be synthesized in the body and therefore are obtained exclusively by consumption. The essential amino acids in humans include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Phenylalanine, one of the essential amino acids, is used in the body to form tyrosine. An enzyme called phenylalanine hydroxylase is involved in adding a hydroxyl group to phenylalanine in what is called a hydroxylation reaction to form tyrosine (Pratt 485). Since tyrosine can be produced in humans in this way, it is considered a nonessential amino acid. Tyrosine is also found in foods such as avocados, pumpkin seeds, bananas, and various dairy products (University of Maryland Medical Center). Plants and bacteria begin the

To synthesize thyroid hormones, an enzyme called thyroid peroxidase combines iodine and tyrosine to form monoiodotyrosine, which is the attachment of one iodine molecule to tyrosine, and diiodotyrosine, the attachment of two iodine molecules (Silverthorn 784). Monoiodotyrosine and diiodotyrosine undergo a condensation reaction to form triiodothyronine, or thyroid hormone T3. Two diiodotyrosine molecules undergo a condensation reaction to form thyroid hormone T4, or thyroxine. Thyroid hormones have metabolic effects on the body and are involved in nervous system development. Because tyrosine is a precursor to thyroid hormones, people who take thyroid hormones are advised to limit consumption of foods that contain tyrosine (University of Maryland Medical Center). Catecholamines - epinephrine, norepinephrine, and dopamine - are derived from tyrosine by the addition of a hydroxyl group with tyrosine hydroxylase followed by the alteration of various functional groups. Catecholamines are involved in the sympathetic nervous