Amino Acids Go Many Different Places
Amino acids have biological functions other than as parts of proteins and oligopeptides. The following examples illustrate some of these functions for a few of the amino acids.
Some products sold in health food stores feature the presence of the branched-chain amino acids isoleucine, leucine, and valine. These are essential amino acids in the sense that the body cannot synthesize them. Under normal circumstances, a diet with adequate protein intake provides enough of all the essential amino acids. Athletes involved in intensive training want to prevent muscle loss and to increase muscle mass. As a result, they take protein supplements and pay particular attention to branched-chain amino acids. (These three amino acids are by no means the only essential ones, but they are mentioned specifically here.)
Monosodium glutamate, or MSG, is a derivative of glutamic acid that finds wide use as a flavor enhancer. MSG causes a physiological reaction in some people, with chills, headaches, and dizziness resulting. Because many Asian foods contain significant amounts of MSG, this problem is often referred to as Chinese restaurantsyndrome.
If the acid group of histidine is removed, it is converted to histamine, which is a potent vasodilator, increasing the diameter of blood vessels. Histamine, which is released as part of the immune response, increases the localized blood volume for white blood cells. This results in the swelling and stuffiness that are associated with a cold. Most cold medications contain antihistamines to overcome this stuffiness.