− | Tryptophan is an essential amino acid for dogs and cats. Tryptophan is classified as an aromatic amino acid and is both gluconeogenic and ketogenic. Unlike the other aromatic amino acids such as [[Phenylalanine and Tyrosine - Nutrition|phenylalanine and tyrosine]], tryptophan has a nitrogen-containing indole side ring. Dietary tryptophan is absorbed by a neutral amino acid transporter in the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] (particularly the [[Jejunum - Anatomy & Physiology|jejunum]]) and plasma tryptophan is actively reabsorbed in the [[Nephron Microscopic Anatomy#Proximal Tubule|proximal tubule]] of the kidney. | + | Tryptophan is an essential amino acid for dogs and cats. Tryptophan is classified as an [[Nutrition Glossary#Aromatic Amino Acids|aromatic amino acid]] and is both gluconeogenic and ketogenic. Unlike the other aromatic amino acids such as [[Phenylalanine and Tyrosine - Nutrition|phenylalanine and tyrosine]], tryptophan has a nitrogen-containing indole side ring. Dietary tryptophan is absorbed by a neutral amino acid transporter in the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] (particularly the [[Jejunum - Anatomy & Physiology|jejunum]]) and plasma tryptophan is actively reabsorbed in the [[Nephron Microscopic Anatomy#Proximal Tubule|proximal tubule]] of the kidney. |