Amino acids are often called the building blocks of life because it takes many of them linked together in a chain to create a protein. DNA tells the body how to make the chain and in what order the amino acids must line up. Some amino acids must be eaten because the body cannot make them (essential), some the body can make (non-essential), and yet others are able to be made during some times, but not others (conditionally essential). The life processes are all dependent on proteins which play critical roles in the body as structure, messengers, enzymes, and hormones.
Proteins are globular and clumpy because the amino acid chains fold in on themselves. This is how the immune system recognizes proteins. They are large compared to single amino acids, and they are uniquely shaped. The immune system does not recognize tiny MSG as an allergen. However, trouble can begin because the body can attack the larger enzymes like GAD, responsible for turning excess MSG into GABA.