How are your enzymes working today? Enzymes are chemical compounds that increase the rate at which reactions take place in a living organism. Without enzymes, most chemical changes in an organism would proceed so slowly that the organism could not survive. As an example, all of the metabolic reactions that take place in the body are made possible by the presence of specific enzymes. As a group these chemical reactions are referred to as metabolism.
So what happens if an enzyme is missing from the body or not functioning as it should? In such cases, a metabolic disorder may develop.
A metabolic disorder is a medical condition that develops when some metabolic reaction essential for normal growth and development does not occur.
The disorder known as phenylketonuria (PKU) is an example. PKU is caused by the lack of an enzyme known as phenylalanine hydroxylase. This enzyme is responsible for converting the amino acid phenylalanine to a second amino acid, tyrosine. Tyrosine is involved in the production of the pigment melanin in the skin. Individuals with PKU are unable to make melanin and are, therefore, usually blond haired and blue eyed.
But PKU has more serious effects than light hair and eye color. When phenylalanine is not converted to tyrosine, it builds up in the body and is converted instead to a compound known as phenylpyruvate. Phenylpyruvate impairs normal brain development, resulting in severe mental retardation in a person with PKU. The worst symptoms of PKU can be prevented if the disorder is diagnosed early in life. In that case, a person can avoid eating foods that contain phenylalanine and developing the disorder that would follow.
Other examples of metabolic disorders include alkaptonuria, thalassemia, porphyria, Tay-Sachs disease, Hurler's syndrome, Gaucher's disease, galactosemia, Cushing's syndrome, diabetes mellitus, hyperthyroidism, and hypothyroidism. At present, no cures for metabolic disorders are available. The best approach is to diagnose such conditions as early as possible and then to arrange a person's diet to deal as effectively as possible with that disorder. Gene therapy appears to have some long-term promise for treating metabolic disorders. In this procedure, scientists attempt to provide those with metabolic disorders with the genes responsible for the enzymes they are missing, thus curing the disorder.
[ See also Metabolism ]