From the Manufacturer:
Glutamine helps replenish muscle glycogen after exercise. Glycogen is a major carbohydrate polysaccharide that is stored in animal cells. Glycogen is formed from glucose and stored in the liver and to a lesser extent muscle cells. Glycogen is depolymerized to glucose and released into circulation as needed by the body. Excess exercise can deplete glycogen from muscle cells. Glutamine may actually help restore the normal levels of glycogen, thus relieving the soreness.
Synthesis of Glutamine from Glutamate is the basic pathway for detoxifying ammonia. Excess of ammonia can generate nitrines (ammonia based free radicals) and are believed to be responsible for neuro-degenerative diseases. In other words Glutamine synthesis in our body may be responsible for protecting our brain as well. Glutamine also helps maintain proper glucose levels and the correct pH range. It also controls the volume of water in individual cells as well.