Valine reveals much about the remarkable precision and harmony in the universe. Similar to leucine and isoleucine, it is a branched-chain amino acid that is found in most animal protein. Because of its structure, valine is important for the correct folding of proteins, and thus tends to be located on the inside of protein molecules. The functionality of a protein is dependent upon its ability to fold into a precise three-dimensional shape.
The necessary precision in protein folding is seen in cases where there are genetic errors. In the case of sickle-cell disease, valine substitutes for the hydrophilic amino acid glutamic acid in hemoglobin. Because valine is hydrophobic, the hemoglobin does not fold correctly.
The normal balance in the universe likewise is emphasized when there is a deficiency of the metabolic enzyme branched chain α-keto acid dehydrogenase (BCKDH). In this case, one gets a buildup of the branched-chain amino acids valine, leucine, and isoleucine in the blood and urine. This is the cause of the serious metabolic disorder maple syrup urine disease.
Being an "essential amino acid," one must get sufficient valine from having a proper diet. That is, it is important for individuals to show discipline in their eating habits. This is particularly the case in maple syrup urine disease, where one must get the minimal levels of valine (and leucine and isoleucine) without too much to cause the disease. This diet must be adhered to strictly and permanently. However, with proper treatment those afflicted are able to live healthy, normal lives and not suffer the severe neurological damage that characterizes the untreated disease.