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Acetylcholine
Acetylcholinesterase (EC 3.1.1.7, e.g. from Torpedo californica, TcAChE) hydrolysizes the neurotransmitter acetylcholine (ACh), producing choline and an acetate group. ACh directly binds Ser200 (via its nucleophilic Oγ atom) within the catalytic triad catalytic triad (Ser200, His440, and Glu327) of (ACh/TcAChE structure 2ace). The residues Trp84 and Phe330 are also important in the ligand recognition. After this binding acetylcholinesterase hydrolysizes ACh.
Acetylcholine Receptors
Nicotinic Acetylcholine Receptors
- Alpha-bungarotoxin is a nicotinic cholinergic antagonist that is found within the venom of Bungarus multicinctus, a South-asian snake belonging to a group commonly known as kraits.
Acetylcholinesterase
Adrenaline (Epinephrine)/Noradrenaline (Norepinephrine)
The adrenergic receptors are metabolic G protein-coupled receptors. They are the targets of catecholamines. The binding of an agonist to them causes a sympathetic response.
- The α-2 adrenergic receptor (A2AR) inhibits insulin or glucagons release.
- The β-1 adrenergic receptor (B1AR) increases cardiac output and secretion of rennin and ghrelin.[2]
- The β-2 adrenergic receptor (B2AR) triggers many relaxation reactions.
Beta-adrenergic receptors
Monoamine oxidases (MAO)
Monoamine oxidases (MAO) (EC 1.4.3.4) are a family of enzymes that catalyze the oxidation of monoamines including adrenaline, noradrenaline, serotonin and dopamine.
Dopamine
Dopamine Receptors
Agonists
- Amphetamine[3]
- Methamphetamine[4]
Antagonists
- Clebopride[5]
- Nafadotride[6]
- Eticlopride.
Structure of the human dopamine D3 receptor in complex with the antagonist eticlopride and maltose (3pbl).
Eticlopride binding site.
Parkinson's disease
DOPA decarboxylase is responsible for the synthesis of dopamine and serotonin from L-DOPA and L-5-hydroxytryptophan, respectively. It is highly stereospecific, yet relatively nonspecific in terms of substrate, making it a somewhat uninteresting enzyme to study. Although it is not typically a rate-determining step of dopamine synthesis, the decarboxylation of L-DOPA to dopamine by DDC is the controlling step for individuals with Parkinson's disease[7], the second most common neurodegenerative disorder, occuring in 1% of the population over the age of 65. The loss of dopaminergic neurons is the main cause of cognitive impairment and tremors observed in patients with the disease. The hallmark of the disease is the formation of alpha-synuclein containing Lewy bodies.
Currently, treatment for the disease is aimed at DOPA decarboxylase inhibition. Since dopamine cannot cross the blood-brain barrier, it cannot be used to directly treat Parkinson's disease. Thus, exogenously administered L-DOPA is the primary treatment for patients suffering from this neurodegenerative disease. Unfortunately, DOPA decarboxylase rapidly converts L-DOPA to dopamine in the blood stream, with only a small percentage reaching the brain. By inhibiting the enzyme, greater amounts of exogenously administered L-DOPA can reach the brain, where it can then be converted to dopamine. [8]. Unfortunately, with continued L-Dopa treatment, up to 80% of patients experience 'wearing-off' symptoms, dyskinesias and other motor complications (referred to as the "on-off phenomenon". [9]. Clearly, a better understanding of the catalytic mechanism and enzymatic activity of DDC in both healthy and PD individuals is critical to drug design and treatment of the disease.
Glutamate
Glutamate receptors
Ionotropic Glutamate Receptors
Ionotropic Glutamate Receptors (IGluRs) are a family of ligand-gated ion channels that are responsible for fast excitatory neurotransmission.[10] Primarily localized to nerve synapses in mammals, IGluRs are implicated in nearly all aspects of nervous system development and function.[11] Synapses form the connection between two neuronal cells. Within synapses, neurotransmitters are released from vesicles in presynaptic cells and interact with receptors in postsynaptic cells to allow for communication between nerve cells.[10] GluR domains include the amino terminal domain (ATD), transmembrane domain (TMD) and ligand-binding domain (LBD). Glutamate is the predominant neurotransmitter of excitatory synapses and interacts specifically with AMPA and NMDA IGluRs.
- AMPA receptor is a non-NMDA-type IGluR
- Kainate receptor (GluK) is a non-NMDA-type IGluR which is activated by the agonist kainate.
- NMDA receptor (NMDAR) is a IGluR which binds to the agonist NMDA. It contains subuntis NR1, NR2A, NR2B, NR2C, NR2D, NR3A, NR3B.
- Ionotropic Glutamate Receptors
- Glutamate receptor (GluA2)
Metabotropic Glutamate Receptors
Metabotropic glutamate receptors are glutamate receptors that activate ion channels indirectly through a signaling cascade involving G proteins[12]. They are members of the large class of seven-transmembrane domain receptors, the G protein-coupled receptors. Glutamate receptors are classified into 3 groups based on their homology, mechanism and pharmacological properties.
AMPA receptors
Histamine
Histamine.
Histamine receptors
Histamine H1 receptor
Neurotensin
Neurotensin receptors
Neurotensin receptor
Serotonin
Serotonin receptors
- ↑ Martin JL, Begun J, McLeish MJ, Caine JM, Grunewald GL. Getting the adrenaline going: crystal structure of the adrenaline-synthesizing enzyme PNMT. Structure. 2001 Oct;9(10):977-85. PMID:11591352
- ↑ Huang J, Chen S, Zhang JJ, Huang XY. Crystal structure of oligomeric beta1-adrenergic G protein-coupled receptors in ligand-free basal state. Nat Struct Mol Biol. 2013 Apr;20(4):419-25. doi: 10.1038/nsmb.2504. Epub 2013 Feb, 24. PMID:23435379 doi:10.1038/nsmb.2504
- ↑ Jones S, Kornblum JL, Kauer JA (August 2000). "Amphetamine blocks long-term synaptic depression in the ventral tegmental area". J. Neurosci. 20 (15): 5575–80. PMID 10908593. https://www.jneurosci.org/cgi/pmidlookup?view=long&pmid=10908593.
- ↑ Cruickshank, CC.; Dyer, KR. (Jul 2009). "A review of the clinical pharmacology of methamphetamine.". Addiction 104 (7): 1085–99. doi:10.1111/j.1360-0443.2009.02564.x. PMID 19426289.
- ↑ Cuena Boy R, Maciá Martínez MA (1998). "[Extrapyramidal toxicity caused by metoclopramide and clebopride: study of voluntary notifications of adverse effects to the Spanish Drug Surveillance System]" (in Spanish). Atencion Primaria 21 (5): 289–95. PMID 9608114. Free full text
- ↑ Pilla M, Perachon S, Sautel F, Garrido F, Mann A, Wermuth CG, Schwartz JC, Everitt BJ, Sokoloff P. Selective inhibition of cocaine-seeking behaviour by a partial dopamine D3 agonist. Nature. 1999;400:371–375.
- ↑ Miles EW. The tryptophan synthase alpha 2 beta 2 complex. Cleavage of a flexible loop in the alpha subunit alters allosteric properties. J Biol Chem. 1991 Jun 15;266(17):10715-8. PMID:1904055
- ↑ Burkhard P, Dominici P, Borri-Voltattorni C, Jansonius JN, Malashkevich VN. Structural insight into Parkinson's disease treatment from drug-inhibited DOPA decarboxylase. Nat Struct Biol. 2001 Nov;8(11):963-7. PMID:11685243 doi:https://dx.doi.org/10.1038/nsb1101-963
- ↑ Miles EW. The tryptophan synthase alpha 2 beta 2 complex. Cleavage of a flexible loop in the alpha subunit alters allosteric properties. J Biol Chem. 1991 Jun 15;266(17):10715-8. PMID:1904055
- ↑ 10.0 10.1 Jin R, Clark S, Weeks AM, Dudman JT, Gouaux E, Partin KM. Mechanism of positive allosteric modulators acting on AMPA receptors. J Neurosci. 2005 Sep 28;25(39):9027-36. PMID:16192394 doi:25/39/9027
- ↑ Sobolevsky AI, Rosconi MP, Gouaux E. X-ray structure, symmetry and mechanism of an AMPA-subtype glutamate receptor. Nature. 2009 Dec 10;462(7274):745-56. Epub . PMID:19946266 doi:10.1038/nature08624
- ↑ Traynelis SF, Wollmuth LP, McBain CJ, Menniti FS, Vance KM, Ogden KK, Hansen KB, Yuan H, Myers SJ, Dingledine R. Glutamate receptor ion channels: structure, regulation, and function. Pharmacol Rev. 2010 Sep;62(3):405-96. doi: 10.1124/pr.109.002451. PMID:20716669 doi:https://dx.doi.org/10.1124/pr.109.002451
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