Ph D Fitness Overview What is L-Glutamine?L-glutamine is an amino acid found in proteins of all life forms. It is classified as a semi-essential or conditionally essential amino acid. L-glutamine is the most abundant amino acid in the body, & plasma glutamine levels are the highest of any amino acid. L-glutamine is predominantly synthesized & stored in skeletal muscle. The amino acid L-glutamate is metabolized to L-glutamine in a reaction catalyzed by the enzyme glutamine synthase, a reaction which, in addition to L-glutamate, requires ammonia, ATP & magnesium. Who needs L-Glutamine? Any athlete taking part in a physically demanding activity that requires a certain level of muscle mass.