True regarding glutamine is:

Glutamine is the most abundant naturally occurring, non-essential amino acid in the human body and one of the only amino acids which directly crosses the blood-brain barrier.In the body it is found circulating in the blood as well as stored in the skeletal muscles. It becomes conditionally essential (requiring intake from food or supplements) in states of illness or injury.Dietary sources of L-glutamine include beef, chicken, fish, eggs, milk and dairy products.Glutamine has a variety of biochemical functions including:- A substrate for DNA synthesis- Major role in protein synthesis- Primary source of fuel for enterocytes (cells lining the inside of the small intestine).- Precursor for rapidly dividing immune cells, thus aiding in immune function- Regulation of acid-base balance in the kidney by producing ammonium- Alternative source of fuel for the brain and helps to block coisol-induced protein catabolism.