Glutamine

Some interesting facts about glutamine:

Glutamine is a conditionally essential amino acid
While glutamine is not an essential amino acid most of the time (essential amino acids are required in the diet as the body cannot manufacture them), there are certain special circumstances which makes it conditionally essential; this means glutamine becomes an essential amino acid under special conditions, especially when intake of the essential amino acid glutamic acid is very low.
Glutamine functions as a building block of protein in the body
Glutamine, just like all the other amino acids, is one of the building blocks of all proteins in the body, which not only include muscles, but also all the other proteins required for normal function of the body.
Glutamine is converted from glutamic acid
The body produces glutamine by synethsising it from glutamic acid, another amino acid which is non-essential.

L-Glutamine supplements are better absorbed and it more closely resembles natural glutamine

Glutamine is used as a source of fuel for some part of the body
Glutamin is important for providing fuel (nitrogen and carbon) to many different cells in the body. It is also required to make glucose (sugar), another form of fuel for the body's cells.
Glutamine is the most abundant amino acid in the body
Glutamine is the most abundant amino acid that is found in the muscles and bloodstream of the body.
L-glutamine is a better supplement to take
The best type of supplemental glutamine to take is L-Glutamine, which is far superior to D-Glutamine, another type of glutamine supplement. L-Glutamine is better absorbed and more closely resembles natural glutamine.