L-DOPA:L-Dihydroxyphenylalanine.:Introduction and Its Benefit Applications.
Contents
L-DOPA Discovery Story.:
The Windsor bean is one of the many varieties of the fava bean (Vicia faba Linnaeus). As a favorite dish, this bean was cultivated in the garden of Fritz Hoffmann, owner of Hoffmann-La Roche Limited. In 1913 a Roche biochemist, Marcus Guggenheim analyzed Windsor beans from Hoffmann's garden. He isolated dihydroxyphenylalanine or dopa. The amino acid was thought biologically inert and little attention was paid to the discovery. ("Therapy for Idiopathic Parkinson's Disease", Irena Rektorova, MD, European Parkinson's Disease Association, 2002)
Almost a century earlier, James Parkinson published an article concerning his observations of three patients suffering from palsy. Parkinson was the first to carefully describe the symptoms of the men, all over age 50. His 1817 An Essay on the Shaking Palsy was so astute that today the disorder carries his name, Parkinson's disease. ("The Story of Shaking Palsy", History of PD, Mayo Clinic)
D-dopa and L-dopa:
Dopa has two forms: dextrorotary or D-dopa and levorotary or L-dopa. The molecules are stereoisomers or mirror-images of each other. In 1938, animal and human studies found an enzyme that converted L-dopa into dopamine. But it would not be discovered until 1960 that people with Parkinson's disease had severe dopamine deficits.
History:
In work that earned him a Nobel Prize in 2000, Swedish scientist Arvid Carlsson first showed in the 1950s that administering levodopa to animals with Parkinsonian symptoms would cause a reduction of the symptoms. The neurologist Oliver Sacks describes this treatment in human patients with encephalitis lethargica in his book Awakenings, upon which the movie of the same name is based.
The 2001 Nobel Prize in Chemistry was also related to L-DOPA: the Nobel Committee awarded one-fourth of the prize to William S. Knowles for his work on chirally-catalysed hydrogenation reactions, the most noted example of which was used for the synthesis of L-DOPA.
Mechanisms:
Levodopa or L-DOPA is an intermediate in dopamine biosynthesis. Clinically, levodopa is used in the management of Parkinson's disease.Research discovered the body converts the amino acid tyrosine into L-dopa; L-dopa is then converted into dopamine. Without the neurotransmitter dopamine to serve a damping effect on neural transmissions, muscles become tense and tremble.
Even though lack of dopamine is the problem, it cannot be given as a treatment. Dopamine cannot cross the barrier between the bloodstream and the brain, but L-dopa can. The enzyme L-dopa decarboxylase changes L-dopa into dopamine in the basal ganglia of the brain.
Since 1966, L-dopa has been the standard treatment to alleviate the symptoms of Parkinson's, but it is not a cure. As the disease progresses, L-dopa eventually fails and causes a host of adverse side-effects. ("Dopamine", William S. Messer, Jr., Medicinal and Biological Chemistry, University of Toledo, 2000)
Levodopa is used as a prodrug to increase dopamine levels for the treatment of Parkinson's disease, since it is able to cross the blood-brain barrier whereas dopamine itself cannot. Once levodopa has entered the central nervous system (CNS), it is metabolized to dopamine by aromatic-L-amino-acid decarboxylase. However, conversion to dopamine also occurs in the peripheral tissues, causing adverse effects and decreasing the available dopamine to the CNS, so it is standard practice to co-administer a peripheral DOPA decarboxylase inhibitor.
In work that earned him a Nobel Prize in 2000, Swedish scientist Arvid Carlsson first showed in the 1950s that administering levodopa to animals with Parkinsonian symptoms would cause a reduction of the symptoms. The 2001 Nobel Prize in Chemistry was also related to L-DOPA: the Nobel Committee awarded one-fourth of the prize to William S. Knowles for his work on chirally catalysed hydrogenation reactions, the most noted example of which was used for the synthesis of L-DOPA.
Reference:
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- 1.L-DOPA:L-Dihydroxyphenylalanine.:Introduction and Its Benefit Applications.
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♣ last edit date:28th,Oct.2010.
