Monoamine oxidases (MAO) are a family of enzymes that catalyze the oxidation of monoamines, employing oxygen to clip off their amine group. They are found bound to the outer membrane of mitochondria in most cell types of the body. The first such enzyme was discovered in 1928 by Mary Bernheim in the liver and was named tyramine oxidase. The MAOs belong to the protein family of flavin-containing amine oxidoreductases.
A catecholamine is a monoamine neurotransmitter, an organic compound that has a catechol and a side-chain amine.
Phenethylamine (PEA) is an organic compound, natural monoamine alkaloid, and trace amine, which acts as a central nervous system stimulant in humans. In the brain, phenethylamine regulates monoamine neurotransmission by binding to trace amine-associated receptor 1 (TAAR1) and inhibiting vesicular monoamine transporter 2 (VMAT2) in monoamine neurons. To a lesser extent, it also acts as a neurotransmitter in the human central nervous system. In mammals, phenethylamine is produced from the amino acid L-phenylalanine by the enzyme aromatic L-amino acid decarboxylase via enzymatic decarboxylation. In addition to its presence in mammals, phenethylamine is found in many other organisms and foods, such as chocolate, especially after microbial fermentation.
Tyramine, also known under several other names, is a naturally occurring trace amine derived from the amino acid tyrosine. Tyramine acts as a catecholamine releasing agent. Notably, it is unable to cross the blood-brain barrier, resulting in only non-psychoactive peripheral sympathomimetic effects following ingestion. A hypertensive crisis can result, however, from ingestion of tyramine-rich foods in conjunction with the use of monoamine oxidase inhibitors (MAOIs).
Selegiline, also known as L-deprenyl and sold under the brand names Eldepryl, Zelapar, and Emsam among others, is a medication which is used in the treatment of Parkinson's disease and major depressive disorder. It has also been studied for a variety of other indications, but has not been formally approved for any other use. The medication in the form licensed for depression has modest effectiveness for this condition that is similar to that of other antidepressants. Selegiline is provided as a swallowed tablet or capsule or an orally disintegrating tablet (ODT) for Parkinson's disease and as a patch applied to skin for depression.
Phenylephrine, sold under the brand names Neosynephrine and Sudafed PE among numerous others, is a medication used as a decongestant for uncomplicated nasal congestion, used to dilate the pupil, used to increase blood pressure, and used to relieve hemorrhoids. It can be taken by mouth, as a nasal spray, given by injection into a vein or muscle, applied to the skin, or as a rectal suppository.
Pargyline, sold under the brand name Eutonyl among others, is a monoamine oxidase inhibitor (MAOI) medication which has been used to treat hypertension but is no longer marketed. It has also been studied as an antidepressant, but was never licensed for use in the treatment of depression. The drug is taken by mouth.
In enzymology, aldose reductase is an enzyme in humans encoded by the gene AKR1B1. It is an cytosolic NADPH-dependent oxidoreductase that catalyzes the reduction of a variety of aldehydes and carbonyls, including monosaccharides, and primarily known for catalyzing the reduction of glucose to sorbitol, the first step in polyol pathway of glucose metabolism.
Oxidative deamination is a form of deamination that generates α-keto acids and other oxidized products from amine-containing compounds, and occurs primarily in the liver. Oxidative deamination is stereospecific, meaning it contains different stereoisomers as reactants and products; this process is either catalyzed by L or D- amino acid oxidase and L-amino acid oxidase is present only in the liver and kidney. Oxidative deamination is an important step in the catabolism of amino acids, generating a more metabolizable form of the amino acid, and also generating ammonia as a toxic byproduct. The ammonia generated in this process can then be neutralized into urea via the urea cycle.
Aldo-keto reductase family 1, member B1 (AKR1B1) is an gene in humans that encodes the enzyme aldose reductase. It is a reduced nicotinamide-adenine dinucleotide phosphate (NADPH)-dependent enzyme catalyzing the reduction of various aldehydes and ketones to the corresponding alcohol. The involvement of AKR1B1 in oxidative stress diseases, cell signal transduction, and cell proliferation process endows AKR1B1 with potential as a therapeutic target.
Alcohol dehydrogenase [NADP+] also known as aldehyde reductase or aldo-keto reductase family 1 member A1 is an enzyme that in humans is encoded by the AKR1A1 gene. AKR1A1 belongs to the aldo-keto reductase (AKR) superfamily. It catalyzes the NADPH-dependent reduction of a variety of aromatic and aliphatic aldehydes to their corresponding alcohols and catalyzes the reduction of mevaldate to mevalonic acid and of glyceraldehyde to glycerol. Mutations in the AKR1A1 gene has been found associated with non-Hodgkin's lymphoma.
Levoamphetamine is a stimulant medication which is used in the treatment of certain medical conditions. It was previously marketed by itself under the brand name Cydril, but is now available only in combination with dextroamphetamine in varying ratios under brand names like Adderall and Evekeo. The drug is known to increase wakefulness and concentration in association with decreased appetite and fatigue. Pharmaceuticals that contain levoamphetamine are currently indicated and prescribed for the treatment of attention deficit hyperactivity disorder (ADHD), obesity, and narcolepsy in some countries. Levoamphetamine is taken by mouth.
3,4-Dihydroxyphenylacetaldehyde (DOPAL), also known as dopamine aldehyde, is a metabolite of the monoamine neurotransmitter dopamine formed by monoamine oxidase (MAO).
The catecholaldehyde hypothesis is a scientific theory positing that neurotoxic aldehyde metabolites of the catecholamine neurotransmitters dopamine and norepinephrine are responsible for neurodegenerative diseases involving loss of catecholaminergic neurons, for instance Parkinson's disease. The specific metabolites thought to be involved include 3,4-dihydroxyphenylacetaldehyde (DOPAL) and 3,4-dihydroxyphenylglycolaldehyde (DOPEGAL), which are formed from dopamine and norepinephrine by monoamine oxidase, respectively. These metabolites are subsequently inactivated and detoxified by aldehyde dehydrogenase (ALDH). DOPAL and DOPEGAL are monoaminergic neurotoxins in preclinical models and inhibition of and polymorphisms in ALDH are associated with Parkinson's disease. The catecholaldehyde hypothesis additionally posits that DOPAL oligomerizes with α-synuclein resulting in accumulation of oligomerized α-synuclein and that this contributes to cytotoxicity.
Imidazole-4-acetaldehyde is a metabolite of histamine in biological species.
The pharmacology of selegiline pertains to the pharmacodynamic and pharmacokinetic properties of the antiparkinsonian and antidepressant selegiline (L-deprenyl). Selegiline is available in a few different forms, including oral tablets and capsules, orally disintegrating tablets (ODTs), and transdermal patches. These forms have differing pharmacological properties.
A monoamine neurotoxin, or monoaminergic neurotoxin, is a drug that selectively damages or destroys monoaminergic neurons. Monoaminergic neurons are neurons that signal via stimulation by monoamine neurotransmitters including serotonin, dopamine, and norepinephrine. Examples of monoamine neurotoxins include the serotonergic neurotoxins para-chloroamphetamine (PCA), methylenedioxymethamphetamine (MDMA), and 5,7-dihydroxytryptamine (5,7-DHT); the dopaminergic neurotoxins oxidopamine (6-hydroxydopamine), MPTP, and methamphetamine; and the noradrenergic neurotoxins oxidopamine and DSP-4. Dopaminergic neurotoxins can induce a Parkinson's disease-like condition in animals and humans. Serotonergic neurotoxins have been associated with cognitive and memory deficits and psychiatric changes.
5-Hydroxyindoleacetaldehyde (5-HIAL), also known as 5-hydroxytryptaldehyde or as serotonin aldehyde, is an inactive metabolite and metabolic intermediate of the monoamine neurotransmitter serotonin.
4-Amino-1-butanol, or 4-aminobutanol, also known as 4-hydroxybutylamine, is an alkanolamine and an analogue and precursor of the neurotransmitter γ-aminobutyric acid (GABA).
A neurotransmitter prodrug, or neurotransmitter precursor, is a drug that acts as a prodrug of a neurotransmitter. A variety of neurotransmitter prodrugs have been developed and used in medicine. They can be useful when the neurotransmitter itself is not suitable for use as a pharmaceutical drug owing to unfavorable pharmacokinetic or physicochemical properties, for instance susceptibility to metabolism or lack of blood–brain barrier permeability. Besides their use in medicine, neurotransmitter prodrugs have also been used as recreational drugs in some cases.
