<unk>  (symbol<unk>  or<unk>  is an α-amino acid that is used in the biosynthesis of proteins. Its side chain is similar to that of<unk> tamic acid, except the carboxylic acid group is replaced by an amide. It is classified as a charge-neutral, polar amino acid. It is non-essential and conditionally essential in humans, meaning the body can usually synthesize sufficient amounts of it, but in some instances of stress, the body's demand for<unk>  increases, and<unk>  must be obtained from the diet. It is encoded by the codons CAA and CAG. In human blood,<unk>  is the most abundant free amino acid. The dietary sources of<unk>  includes especially the protein-rich foods like beef, chicken, fish, dairy products, eggs, vegetables like beans, beets, cabbage, spinach, carrots, parsley, vegetable juices and also in wheat, papaya, Brussels sprouts, celery, kale and fermented foods like miso.
Glutamine
Inositol
Choline
Gluten
Nicotinamide
Cysteamine
Glutamate 
Phenserine