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==What are Phenylalanine and Tyrosine?==

==What are Phenylalanine and Tyrosine?==

Phenylalanine and tyrosine are '''[[Nutrition Glossary#Aromatic Amino Acids|aromatic amino acids]] each containing a benzene ring side chain'''. Phenylalanine is converted to tyrosine in both dogs and cats and '''only phenylalanine is considered an essential amino acid'''. Tyrosine production accounts for half of the total phenylalanine requirement in the diet<ref name ="Milner">Milner JA. Phenylalanine and tyrosine requirement in immature beagle dogs. J Nutr 1984;114:2212-2216.</ref>, and both amino acids are considered together when determining the daily requirement. Phenylalanine is converted directly to tyrosine via phenylalanine hydroxylase in the [[Liver - Anatomy & Physiology|liver]]; this is a non-reversible step in phenylalanine degradation. The addition of dietary tyrosine can “spare” phenylalanine reducing the phenylalanine requirement. Phenylalanine and tyrosine are '''neutral amino acids and are both gluconeogenic and ketogenic'''. They are absorbed by a neutral amino acid transporter in the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] (particularly the [[Jejunum - Anatomy & Physiology|jejunum]]) and are actively reabsorbed in the [[Nephron Microscopic Anatomy#Proximal Tubule|proximal tubule]] of the kidney.

Phenylalanine and tyrosine are '''[[Nutrition Glossary#Aromatic Amino Acids|aromatic amino acids]] each containing a benzene ring side chain'''. Phenylalanine is converted to tyrosine in both dogs and cats and '''only phenylalanine is considered an essential amino acid'''. Tyrosine production accounts for half of the total phenylalanine requirement in the diet<ref name ="Milner">Milner JA. Phenylalanine and tyrosine requirement in immature beagle dogs. J Nutr 1984;114:2212-2216.</ref>, and both amino acids are considered together when determining the daily requirement. Phenylalanine is converted directly to tyrosine via phenylalanine hydroxylase in the [[Liver - Anatomy & Physiology|liver]]; this is a non-reversible step in phenylalanine degradation. The addition of dietary tyrosine can “spare” phenylalanine reducing the phenylalanine requirement. Phenylalanine and tyrosine are '''neutral amino acids and are both [[Amino Acids Overview - Nutrition|gluconeogenic and ketogenic]]'''. They are absorbed by a neutral amino acid transporter in the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] (particularly the [[Jejunum - Anatomy & Physiology|jejunum]]) and are actively reabsorbed in the [[Nephron Microscopic Anatomy#Proximal Tubule|proximal tubule]] of the kidney.

==Why are they Important?==

==Why are they Important?==