Catecholamine
106293
221943967
2008-06-26T20:18:04Z
Liaocyed
475529
/* Synthesis */
[[Image:Adrenalin - Adrenaline.svg|thumb|[[epinephrine]]]]
[[Image:Noradrenalin - Noradrenaline.svg|thumb|[[norepinephrine]]]]
[[Image:Dopamin - Dopamine.svg|thumb|[[dopamine]]]]
'''Catecholamines''' are [[chemical compound]]s derived from the [[amino acid]] [[tyrosine]] containing [[catechol]] and [[amine]] groups. Some of them are [[biogenic amine]]s. Catecholamines are water-soluble and are 50% bound to plasma proteins, so they circulate in the bloodstream. The most abundant catecholamines are [[epinephrine]] (adrenaline), [[norepinephrine]] (noradrenaline) and [[dopamine]], all of which are produced from [[phenylalanine]] and tyrosine. Tyrosine is created from phenylalanine by [[hydroxylation]] by the enzyme [[phenylalanine hydroxylase]] (tyrosine is also ingested directly from dietary protein). Tyrosine is then sent to catecholamine-secreting neurons. Here, many kinds of reactions convert it to dopamine, to norepinephrine, and eventually to epinephrine.<ref>[http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=3473965&dopt=Abstract Dopamine beta-hydroxylase: biochemistry and molecu...[Ann N Y Acad Sci. 1987] - PubMed Result<!-- Bot generated title -->]</ref> Catecholamines are [[hormones]] that are released by the [[adrenal glands]] in situations of stress such as [[Fight-or-flight response|psychological stress]] or [[low blood sugar]] levels.<ref>[http://www.consciouschoice.com/1999/cc1207/hmd1207.html "Hypoglycemia"] by Ronald Hoffman, M.D., July 1999, The Holistic M.D.</ref>
==Production==
===Location===
Catecholamines are produced mainly by the [[chromaffin cells]] of the [[adrenal medulla]] and the [[postganglionic fiber]]s of the [[sympathetic nervous system]]. [[Dopamine]], which acts as a [[neurotransmitter]] in the [[central nervous system]], is largely produced in neuronal cell bodies in two areas of the brainstem: the [[substantia nigra]] and the [[ventral tegmental area]].
===Synthesis===
Dopamine is the first cathecholamine to be synthesised from steps shown. Norepinephrine and epinephrine, in turn, are derived from further modifications of dopamine. It is important to note that the enzyme dopamine hydroxylase requires copper as a cofactor (not shown) and DOPA decarboxylase requires [[Pyridoxal phosphate|PLP]] (not shown).
[[Image:Catecholamines biosynthesis.svg|thumb|400px|center|Catecholamine synthesis.]]
Catecholamine synthesis is inhibited by ''alpha-Methyltyrosine'', by inhibiting tyrosine-3 monooxygenase.<ref>[http://www.wrongdiagnosis.com/medical/alpha_methyltyrosine.htm wrongdiagnosis.com] - Description of Alpha-Methyltyrosine</ref>
==Function==
===Modality===
Two catecholamines, [[norepinephrine]] and [[dopamine]], act as [[neuromodulators]] in the [[central nervous system]] and as hormones in the blood circulation. The catecholamine [[norepinephrine]] is a neuromodulator of the peripheral sympathetic nervous system but is also present in the blood (mostly through "spillover" from the [[synapse]]s of the sympathetic system).
High catecholamine levels in blood are associated with [[Stress (medicine)|stress]], which can be induced from psychological reactions or environmental stressors such as [[noise health effects|elevated sound levels]], [[light pollution|intense light]], or [[Hypoglycemia|low blood sugar levels]].
Extremely high levels of catecholamine (also known as catecholamine toxicity) can occur in [[central nervous system]] trauma due to stimulation and/or damage of [[nucleus (neuroanatomy)|nuclei]] in the [[brainstem]], in particular those nuclei affecting the [[sympathetic nervous system]]. In [[emergency medicine]], this occurrence is widely known as ''catecholamine dump''.
Extremely high levels of catecholamine can also be caused by [[neuroendocrine tumor]]s in the [[adrenal medulla]], a treatable condition known as [[pheochromocytoma]].
===Effects===
Catecholamines cause general physiological changes that prepare the body for physical activity ([[fight-or-flight response]]). Some typical effects are increases in [[heart rate]], [[blood pressure]], [[blood glucose]] levels, and a general reaction of the [[sympathetic nervous system]]. Some drugs, like [[tolcapone]] (a central [[COMT]]-inhibitor), raise the levels of all the catecholamines.
===Function in plants===
<blockquote>"They have been found in 44 plant families, but no essential metabolic function has been established for them. They are precursors of benzo[c]phenanthridine [[alkaloid]]s, which are the active principal ingredients of many [[medicinal plant]] extracts. CAs have been implicated to have a possible protective role against insect predators, injuries, and nitrogen detoxification. They have been shown to promote plant tissue growth, somatic embryogenesis from in vitro cultures, and flowering. CAs inhibit indole-3-acetic acid oxidation and enhance [[ethylene]] biosynthesis. They have also been shown to enhance synergistically various effects of [[gibberellin]]s."<ref>[http://www.springerlink.com/content/x8t5q3w1840641p6/ A. I. Kuklin and B. V. Conger, "Catecholamines in plants," Journal of Plant Growth Regulation], Springer New York ISSN 0721-7595 (Print), ISSN 1435-8107 (Online), Issue Volume 14, Number 2 / June, 1995 DOI 10.1007/BF00203119, pp. 91-97.</ref></blockquote>
==Structure==
Catecholamines have the distinct structure of a [[benzene ring]] with two [[hydroxyl]] groups, an intermediate [[ethyl]] chain, and a terminal [[amine]] group.
==Degradation==
They have a half-life of approximately a few minutes when circulating in the blood.
Monoamine oxidase ([[MAO]]) is the main enzyme responsible for degradation of catecholamines.
[[Methamphetamine]] and [[MAOI]]s bind in order for MAOs to inhibit their action of breaking down catecholamines. This is primarily the reason why the effects of amphetamines have a longer lifespan than those of [[cocaine]] and other substances. [[Amphetamines]] not only cause a release of [[dopamine]], [[epinephrine]], and [[norepinephrine]] into the blood stream but also suppress re-absorption.
==See also==
<div class="references-small" style="-moz-column-count:2; column-count:2;">
*[[Catechol-O-methyl transferase]]
*[[Hormone]]
*[[Julius Axelrod]]
*[[Phenethylamine]]s
*[[Steroid hormone]]
*[[Peptide hormone]]
*[[Sympathomimetics]]
*[[Vanillyl mandelic acid]]
</div>
==References==
<references/>
==External links==
* {{MeshName|Catecholamines}}
[[Category:Benzenediols]]
[[Category:Biogenic amines]]
[[Category:Catecholamines|*]]
[[Category:Neurotransmitters]]
[[Category:Sympathomimetics]]
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