Disorders Of Dopamine Metabolism

It takes several steps to make dopamine and there are several enzymes involved. If you have problems creating any of the enzymes, there will be problems metabolizing dopamine. This may result in a dopamine deficiency. In Parkinson's disease, the nerves in the brain that contain dopamine degenerate and you may experience tremors, and stiff muscles and abnormal movements. Disorders of dopamine metabolism may have some symptoms that are similar.

Dopamine Metabolism

An enzyme named phenylalanine hydroxylase, mainly found in the liver, is needed to change the amino acid phenylalanine to the amino acid tyrosine, as explained in "Goodman & Gilman's The Pharmacological Basis of Therapeutics," by Elaine Sanders-Bush, Ph.D. A professor emerita of pharmacology at Vanderbilt University School of Medicine, Sanders-Bush explains that an enzyme is a protein needed by cells to make a biochemical reaction go faster. The enzyme tyrosine hydroxylase is then used to change tyrosine to levadopa. This L-DOPA is quickly changed to dopamine by the enzyme aromatic L-amino acid decarboxylase (AADC).

Parkinsonism and Dopamine Metabolism

The phenylalanine hydroxylase and tyrosine hydroxylase enzymes cannot function in the absence of a substance called tetrahydrobiopterin. In an article published in the June 2007 issue of the "Journal of Nutrition," Keith Hyland explains that if you do not have enough tetrahydrobiopterin, you will not, therefore, be able to make enough dopamine. A deficiency of dopamine can lead to Parkinsonism. In Parkinson's disease, the nerves in the substantia nigra area of the brain degenerate. These are the nerves that contain dopamine, but a deficiency of tetrahydrobiopterin may lead to an L-DOPA deficiency, dopamine deficiency and Parkinsonism, where the symptoms are similar to Parkinson's disease.

Segawa's Syndrome

People with Segawa's syndrome do not have enough of an enzyme called guanosine triphosphate, or GTP, cyclohydrolase. This enzyme is necessary for the cells to be able to make tetrahydrobiopterin. The enzyme deficiency creates a domino effect, for without enough GTP cyclohydrolase, there will not be enough tetrahydrobiopterin, which means there will be an insufficient quantity of phenylalanine hydroxylase and tyrosine hydroxylase, and not enough dopamine. The University of Utah School of Medicine explains that this is a genetic disorder, also referred to as dopa-responsive dystonia. You may experience tremors and writer's cramp, and make abnormal leg movements, especially after exercise or at the end of the day.

Aromatic L-Amino Acid Decarboxylase Deficiency

The AADC enzyme is needed to change L-DOPA to dopamine. Thus, a deficiency of this enzyme may cause a dopamine deficiency. According to the National Institutes of Health, this deficiency comprises a rare hereditary disease where an infant will have symptoms before she is 1 year old. She may have problems sleeping and eating; have stiff muscles, and little energy; make involuntary movements; while at the same time have a hard time moving. When she gets older, she may have muscle spasms, reflux, abnormal eye movements, low blood sugar and low blood pressure as well as pain.