L-DOPA is a chemical that is made and used as part of the normal
biologyBiology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
of some animals and plants. Some animals including humans make it via
biosynthesisBiosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...
from the
amino acidAmino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
L-tyrosine.
L-DOPA is the
precursorIn chemistry, a precursor is a compound that participates in the chemical reaction that produces another compound. In biochemistry, the term "precursor" is used more specifically to refer to a chemical compound preceding another in a metabolic pathway....
to the
neurotransmitterNeurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
s
dopamineDopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...
,
norepinephrineNorepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...
(noradrenaline), and
epinephrineEpinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...
(adrenaline) collectively known as
catecholamineCatecholamines are molecules that have a catechol nucleus consisting of benzene with two hydroxyl side groups and a side-chain amine. They include dopamine, as well as the "fight-or-flight" hormones adrenaline and noradrenaline released by the adrenal medulla of the adrenal glands in response to...
s.
L-DOPA can be manufactured and in its pure form is sold as a
psychoactive drugA psychoactive drug, psychopharmaceutical, or psychotropic is a chemical substance that crosses the blood–brain barrier and acts primarily upon the central nervous system where it affects brain function, resulting in changes in perception, mood, consciousness, cognition, and behavior...
with the
INNAn International Nonproprietary Name is the official nonproprietary or generic name given to a pharmaceutical substance, as designated by the World Health Organization...
levodopa; trade names include
Sinemet,
Parcopa,
Atamet,
Stalevo,
Madopar,
Prolopa, etc.). As a drug it is used in the clinical
treatmentThis is a list of types of therapy .* Adventure therapy* Animal-assisted therapy* Aquatic therapy* Aromatherapy* Art and dementia* Art therapy* Authentic Movement* Behavioral therapy* Bibliotherapy* Buteyko Method* Chemotherapy...
of
Parkinson's diseaseParkinson's disease is a degenerative disorder of the central nervous system...
and
dopamine-responsive dystoniaDopamine-responsive dystonia , also known as hereditary progressive dystonia with diurnal fluctuation, Segawa's disease, or Segawa's dystonia, is a genetic movement disorder which usually manifests itself during early childhood at around ages 5–8 years .Characteristic symptoms are increased muscle...
.
Therapeutic use
L-DOPA crosses the protective
blood-brain barrierThe blood–brain barrier is a separation of circulating blood and the brain extracellular fluid in the central nervous system . It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion...
, whereas dopamine itself cannot. Thus,
L-DOPA is used to increase dopamine
concentrationIn chemistry, concentration is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration...
s in the treatment of
Parkinson's diseaseParkinson's disease is a degenerative disorder of the central nervous system...
and
dopamine-responsive dystoniaDopamine-responsive dystonia , also known as hereditary progressive dystonia with diurnal fluctuation, Segawa's disease, or Segawa's dystonia, is a genetic movement disorder which usually manifests itself during early childhood at around ages 5–8 years .Characteristic symptoms are increased muscle...
. This treatment was originally developed by
George CotziasGeorge C. Cotzias was a Greek-American scientist who together with his coworkers developed L-Dopa treatment, currently the most commonly used treatment for Parkinson's disease....
and his coworkers. Once
L-DOPA has entered the
central nervous systemThe central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
, it is converted into dopamine by the
enzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
aromatic L-amino acid decarboxylaseAromatic L-amino acid decarboxylase is a lyase enzyme.-Reactions:It catalyzes several different decarboxylation reactions:* L-DOPA to dopamine - a neurotransmitter* 5-HTP to serotonin - also a neurotransmitter...
, also known as DOPA decarboxylase (DDC). Pyridoxal phosphate (vitamin B6) is a required
cofactorA cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. These proteins are commonly enzymes, and cofactors can be considered "helper molecules" that assist in biochemical transformations....
in this
reactionA chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
, and may occasionally be administered along with
L-DOPA, usually in the form of
pyridoxinePyridoxine is one of the compounds that can be called vitamin B6, along with pyridoxal and pyridoxamine. It differs from pyridoxamine by the substituent at the '4' position. It is often used as 'pyridoxine hydrochloride'.-Chemistry:...
.
Besides the CNS,
L-DOPA is also converted into dopamine from within the
peripheral nervous systemThe peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...
. The resulting hyperdopaminergia causes many of the adverse
side effectIn medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...
s seen with sole
L-DOPA administration. In order to bypass these effects, it is standard clinical practice to co-administer (with
L-DOPA) a peripheral
DOPA decarboxylase inhibitorAn aromatic L-amino acid decarboxylase inhibitor is a drug which inhibits the synthesis of dopamine by the enzyme aromatic L-amino acid decarboxylase ....
(DDCI) such as
carbidopaCarbidopa is a drug given to people with Parkinson's disease in order to inhibit peripheral metabolism of levodopa.- Pharmacology :...
(medicines combining
L-DOPA and carbidopa are branded as Lodosyn, Sinemet, Parcopa, Atamet, Stalevo) or with a
benserazideBenserazide is a peripherally-acting aromatic L-amino acid decarboxylase or DOPA decarboxylase inhibitor, which is unable to cross the blood-brain barrier.- Indications :...
(combination medicines are branded Madopar, Prolopa), to prevent the peripheral synthesis of dopamine from
L-DOPA. Co-administration of
pyridoxinePyridoxine is one of the compounds that can be called vitamin B6, along with pyridoxal and pyridoxamine. It differs from pyridoxamine by the substituent at the '4' position. It is often used as 'pyridoxine hydrochloride'.-Chemistry:...
without a DDCI accelerates the peripheral
decarboxylationDecarboxylation is a chemical reaction that releases carbon dioxide . Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis, is called carbonation, the addition of CO2 to...
of
L-DOPA to such an extent that it negates the effects of
L-DOPA administration, a phenomenon that historically caused great confusion.
In addition,
L-DOPA, co-administered with a peripheral DDCI, has been investigated as a potential treatment for restless leg syndrome. However,
studiesResearch can be defined as the scientific search for knowledge, or as any systematic investigation, to establish novel facts, solve new or existing problems, prove new ideas, or develop new theories, usually using a scientific method...
have demonstrated "no clear picture of reduced symptoms".
There are two types of response seen with administration of
L-DOPA:
- Short-duration response, which is related to the half-life of the drug
- Longer-duration response, which depends on the accumulation of effects over at least two weeks. This response is evident only in early therapy, as the inability of the brain to store dopamine is not yet a concern.
Dietary supplements
Herbal extractsA dietary supplement, also known as food supplement or nutritional supplement, is a preparation intended to supplement the diet and provide nutrients, such as vitamins, minerals, fiber, fatty acids, or amino acids, that may be missing or may not be consumed in sufficient quantities in a person's diet...
containing
L-DOPA are available. The most common
plantPlants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
sourceNatural resources occur naturally within environments that exist relatively undisturbed by mankind, in a natural form. A natural resource is often characterized by amounts of biodiversity and geodiversity existent in various ecosystems....
of
L-DOPA marketed in this manner is
Mucuna pruriensMucuna pruriens is a tropical legume known as velvet bean or cowitch and by other common names , found in Africa, India and the Caribbean. The plant is infamous for its extreme itchiness produced on contact, particularly with the young foliage and the seed pods...
(Velvet Bean).
Biological role
L-DOPA is produced from the amino acid
L-
tyrosineTyrosine or 4-hydroxyphenylalanine, is one of the 22 amino acids that are used by cells to synthesize proteins. Its codons are UAC and UAU. It is a non-essential amino acid with a polar side group...
by the enzyme
tyrosine hydroxylaseTyrosine hydroxylase or tyrosine 3-monooxygenase is the enzyme responsible for catalyzing the conversion of the amino acid L-tyrosine to dihydroxyphenylalanine . It does so using tetrahydrobiopterin as a coenzyme. DOPA is a precursor for dopamine, which, in turn, is a precursor for norepinephrine ...
(TH). It is also the precursor for the monoamine or
catecholamineCatecholamines are molecules that have a catechol nucleus consisting of benzene with two hydroxyl side groups and a side-chain amine. They include dopamine, as well as the "fight-or-flight" hormones adrenaline and noradrenaline released by the adrenal medulla of the adrenal glands in response to...
neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline). Dopamine is formed by the decarboxylation of
L-DOPA.
L-DOPA can be directly metabolized by
catechol-O-methyl transferaseCatechol-O-methyltransferase is one of several enzymes that degrade catecholamines such as dopamine, epinephrine, and norepinephrine. In humans, catechol-O-methyltransferase protein is encoded by the COMT gene...
(COMT) to 3-O-methyldopa (3-OMD), and then further to vanillactic acid (VLA). This metabolic pathway is non-existent in the healthy body, but becomes important after peripheral
L-DOPA administration in patients with PD or in the rare cases of patients with
aromatic L-amino acid decarboxylaseAromatic L-amino acid decarboxylase is a lyase enzyme.-Reactions:It catalyzes several different decarboxylation reactions:* L-DOPA to dopamine - a neurotransmitter* 5-HTP to serotonin - also a neurotransmitter...
(AADC) enzyme deficiency.
The prefix
L- references its property of levorotation (compared with dextrorotation or
D-DOPAD-DOPA is similar to L-DOPA , but with opposite chirality. Levo- and dextro- rotation reference a molecule's ability to rotate planes of polarized light in either direction...
).
L-Phenylalanine,
L-tyrosine, and
L-DOPA, are all are precursors to the biological
pigmentA pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
melaninMelanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...
. The enzyme
tyrosinaseTyrosinase also known as monophenol monooxygenase is an enzyme that catalyses the oxidation of phenols and is widespread in plants and animals...
catalyzes the oxidation of
L-DOPA to the reactive intermediate dopaquinone, which reacts further, eventually leading to melanin
oligomerIn chemistry, an oligomer is a molecule that consists of a few monomer units , in contrast to a polymer that, at least in principle, consists of an unlimited number of monomers. Dimers, trimers, and tetramers are oligomers. Many oils are oligomeric, such as liquid paraffin...
s.
Side effects
The side effects of
L-DOPA may include, but not limited to:
- Hypotension
In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
, especially if the dosage is too high
- Arrhythmias, although these are uncommon
- Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
, which is often reduced by taking the drug with food, although proteinProteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
interferes with drug absorption
- Gastrointestinal bleeding
- Disturbed respiration
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
, which is not always harmful, and can actually benefit patients with upper airway obstruction
- Hair loss
Alopecia means loss of hair from the head or body. Alopecia can mean baldness, a term generally reserved for pattern alopecia or androgenic alopecia. Compulsive pulling of hair can also produce hair loss. Hairstyling routines such as tight ponytails or braids may induce Traction alopecia. Both...
- Disorientation and confusion
Confusion of a pathological degree usually refers to loss of orientation sometimes accompanied by disordered consciousness and often memory Confusion (from Latin confusĭo, -ōnis, noun of action from confundere "to pour together", also "to confuse") of a pathological degree usually refers to loss...
- Extreme emotion
Emotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...
al states, particularly anxietyAnxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...
, but also excessive libidoLibido refers to a person's sex drive or desire for sexual activity. The desire for sex is an aspect of a person's sexuality, but varies enormously from one person to another, and it also varies depending on circumstances at a particular time. A person who has extremely frequent or a suddenly...
- Vivid dream
Dreams are successions of images, ideas, emotions, and sensations that occur involuntarily in the mind during certain stages of sleep. The content and purpose of dreams are not definitively understood, though they have been a topic of scientific speculation, philosophical intrigue and religious...
s and/or insomniaInsomnia is most often defined by an individual's report of sleeping difficulties. While the term is sometimes used in sleep literature to describe a disorder demonstrated by polysomnographic evidence of disturbed sleep, insomnia is often defined as a positive response to either of two questions:...
- Auditory
An auditory hallucination, or paracusia, is a form of hallucination that involves perceiving sounds without auditory stimulus. A common form involves hearing one or more talking voices...
and/or visual hallucinations
- Effects on learning; there is some evidence that it improves working memory
Working memory has been defined as the system which actively holds information in the mind to do verbal and nonverbal tasks such as reasoning and comprehension, and to make it available for further information processing...
, while impairing other complex functions
- Somnolence
Somnolence is a state of near-sleep, a strong desire for sleep, or sleeping for unusually long periods . It has two distinct meanings, referring both to the usual state preceding falling asleep, and the chronic condition referring to being in that state independent of a circadian rhythm...
and narcolepsyNarcolepsy is a chronic sleep disorder, or dyssomnia, characterized by excessive sleepiness and sleep attacks at inappropriate times, such as while at work. People with narcolepsy often experience disturbed nocturnal sleep and an abnormal daytime sleep pattern, which often is confused with insomnia...
- A condition similar to stimulant psychosis
Although there are many adverse effects associated with
L-DOPA, in particular psychiatric ones, it has fewer than other antiparkinsonian agents, such as
anticholinergicAn anticholinergic agent is a substance that blocks the neurotransmitter acetylcholine in the central and the peripheral nervous system. An example of an anticholinergic is dicycloverine, and the classic example is atropine....
s and dopamine receptor agonists.
More serious are the effects of chronic levodopa administration in the treatment of Parkinson disease, which include:
- End-of-dose deterioration of function
- On/off oscillations
- Freezing during movement
- Dose failure (drug resistance
Drug resistance is the reduction in effectiveness of a drug such as an antimicrobial or an antineoplastic in curing a disease or condition. When the drug is not intended to kill or inhibit a pathogen, then the term is equivalent to dosage failure or drug tolerance. More commonly, the term is used...
)
- Dyskinesia
Dyskinesia is a movement disorder which consists of effects including diminished voluntary movements and the presence of involuntary movements, similar to tics or choreia. Dyskinesia can be anything from a slight tremor of the hands to uncontrollable movement of, most commonly, the upper body but...
at peak dose
- Possible serotonin
Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...
depletion: Recent studies have demonstrated that use of L-DOPA without simultaneously giving proper levels of serotonin precursors depletes serotonin
- Possible dopamine dysregulation: The long-term use of L-DOPA in PD has been linked to the so-called dopamine dysregulation syndrome
Dopamine dysregulation syndrome , sometimes known as hedonistic homeostatic dysregulation in Parkinson's disease, is a dysfunction of the reward system in subjects with Parkinson's disease due to a long exposure to dopamine replacement therapy...
.
Clinicians will try to avoid these side effects by limiting
L-DOPA doses as much as possible until absolutely necessary.
Toxicity
Some scientific studies suggest a cytotoxic role in the promotion and occurrence of adverse effects associated with
L-DOPA treatment. Though the drug is generally safe in humans, some researchers have reported an increase in
cytotoxicityCytotoxicity is the quality of being toxic to cells. Examples of toxic agents are a chemical substance, an immune cell or some types of venom .-Cell physiology:...
markers in
ratRats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
pheochromocytoma PC12 cell lines treated with
L-DOPA. Other authors have attributed the observed toxic effects of
L-DOPA in neural
dopamineDopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...
cell lines to enhanced formation of quinones through increased auto-oxidation and subsequent cell death in mesencephalic cell cultures. Though
L-DOPA is generally considered safe, some controversy surrounds its use in the treatment of PD, given some data indicating a deleterious effect on
intracellularNot to be confused with intercellular, meaning "between cells".In cell biology, molecular biology and related fields, the word intracellular means "inside the cell".It is used in contrast to extracellular...
and neuronal tissue involved in the
pathogenesisThe pathogenesis of a disease is the mechanism by which the disease is caused. The term can also be used to describe the origin and development of the disease and whether it is acute, chronic or recurrent...
of the
diseaseA disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
.
History
In work that earned him a
Nobel PrizeThe Nobel Prize in Physiology or Medicine administered by the Nobel Foundation, is awarded once a year for outstanding discoveries in the field of life science and medicine. It is one of five Nobel Prizes established in 1895 by Swedish chemist Alfred Nobel, the inventor of dynamite, in his will...
in 2000, Swedish scientist
Arvid CarlssonArvid Carlsson is a Swedish scientist who is best known for his work with the neurotransmitter dopamine and its effects in Parkinson's disease...
first showed in the 1950s that administering
L-DOPA to animals with Parkinsonian
symptomA symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
s would cause a reduction in their intensity. This treatment was later extended to manganese poisoning and later Parkinsonism by
George CotziasGeorge C. Cotzias was a Greek-American scientist who together with his coworkers developed L-Dopa treatment, currently the most commonly used treatment for Parkinson's disease....
and his coworkers, who greatly increased the dose. The
neurologistNeurology is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue,...
Oliver SacksOliver Wolf Sacks, CBE , is a British neurologist and psychologist residing in New York City. He is a professor of neurology and psychiatry at Columbia University, where he also holds the position of Columbia Artist...
describes this treatment in human patients with
encephalitis lethargicaEncephalitis lethargica or von Economo disease is an atypical form of encephalitis. Also known as "sleepy sickness" , it was first described by the neurologist Constantin von Economo in 1917. The disease attacks the brain, leaving some victims in a statue-like condition, speechless and motionless...
in his book
AwakeningsAwakenings is a 1973 non-fiction book by Oliver Sacks. It recounts the life histories of those who had been victims of the 1920s encephalitis lethargica epidemic. Sacks chronicles his efforts in the late 1960s to help these patients at the Beth Abraham Hospital in the Bronx, New York. The...
, upon which
the movie of the same nameAwakenings is a 1990 American drama film based on Oliver Sacks's 1973 memoir Awakenings. It tells the true story of British neurologist Oliver Sacks, fictionalized as American Malcolm Sayer and portrayed by Robin Williams who, in 1969, discovers beneficial effects of the then-new drug L-Dopa...
is based.
The 2001
Nobel Prize in ChemistryThe Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...
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
hydrogenationHydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...
reactions, the most noted example of which was used for the synthesis of
L-DOPA:
Marine adhesion
L-DOPA is a key
compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
in the formation of
marineMarine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
adhesiveAn adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials...
proteinProteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s, such as those found in
musselThe common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
s. It is believed to be responsible for the water-resistance and rapid curing abilities of these proteins.
L-DOPA may also be used to prevent surfaces from fouling by bonding antifouling polymers to a susceptible
substrateIn biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...
.
See also
- D-DOPA
D-DOPA is similar to L-DOPA , but with opposite chirality. Levo- and dextro- rotation reference a molecule's ability to rotate planes of polarized light in either direction...
(Dextrodopa)
- L-DOPS (Droxidopa)
- Methyldopa
Methyldopa is an alpha-adrenergic agonist psychoactive drug used as a sympatholytic or antihypertensive. Its use is now mostly deprecated following the introduction of alternative safer classes of agents...
(Aldomet, Apo-Methyldopa, Dopamet, Novomedopa, etc.)
- Dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...
(Intropan, Inovan, Revivan, Rivimine, Dopastat, Dynatra, etc.)
- Norepinephrine
Norepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...
(Noradrenaline; Levophed, etc.)
- Epinephrine
Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...
(Adrenaline; Adrenalin, EpiPen, Twinject, etc.)
External links