Background on Glutamine. A conditionally essential amino acid, glutamine is made from glutamic acid, another amino acid, by the action of the enzyme glutamine synthetase. The majority of glutamine is stored in skeletal muscle tissue, with the remainder in the lungs, liver, brain, and stomach.ackground on Glutamine. A conditionally essential amino acid, glutamine is made from glutamic acid, another amino acid, by the action of the enzyme glutamine synthetase. The majority of glutamine is stored in skeletal muscle tissue, with the remainder in the lungs, liver, brain, and stomach.