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Enzyme or Protein | Biochemistry | Syndromes |
Phenylalanine hydroxylase
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L-phenylalanine to L-tyrosine | Phenylketonuria
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Tyrosine hydroxylase
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L-tyrosine to L-DOPA |
L-DOPA responsive dystonia |
L-aromatic amino acid decarboxylase ![]() ![]() |
L-DOPA to dopamine; 5OH-tryptophan to serotonin |
Neonatal seizures; Hypotonia; Infantile death |
Dopamine ![]() ![]() |
Dopamine to Norepinephrine | Orthostatic
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Monoamine ![]() ![]() |
Norepinephrine to dihydroxyphenylglycol With aldehyde reductase ![]() ![]() |
Brunner syndrome
![]() Retardation: Mild Impulsive behavior |
Monoamine ![]() ![]() |
Norepinephrine to dihydroxyphenylglycol With aldehyde reductase ![]() ![]() |
? asymptomatic
![]() Linkage: Norrie syndrome ![]() |
Catechol-O- Methyltransferase ![]() ![]() |
Degradation of dopamine, epinephrine and norepinephrine |
? asymptomatic
![]() Linkage: Velo-cardio-facial ![]() DeGeorge syndrome ![]() |
Copper-transporting ATPase 1 ![]() ![]() ![]() |
ATP
to ADP Reduced DβH activity |
Menkes
![]() Occipital horn ![]() SMAX3 |
GTP-cyclohydrolase 1
![]() ![]() ![]() |
Biopterin H4 synthesis: Step 1 GTP to D-erythro-7,8- dihydroneopterin (PO4)3 |
L-DOPA responsive dystonia ![]() Hyperphenylalaninemia: Severe ![]() |
Dihydropteridine ![]() ![]() |
Biopterin H2 to |
Phenyketonuria: Atypical ![]() |
Carbinolamine ![]() ![]() ![]() |
4a-OH-Biopterin H4 to Biopterin H2 |
Phenyketonuria: Mild ![]() |
Tyrosinase
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Tyrosine to Dopaquinone | Albinism
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Phenolsulfotransferase
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Catecholamine inactivator by sulfoconjugation |
? |
Norepinephrine ![]() (SLC6A2 ![]() |
Removes NE from synaptic cleft |
Orthostatic Intolerance
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Dopamine receptor D2
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Neuroleptic receptor |
Myoclonus dystonia (DYT11)
![]() Polymorphism: ↓ Risk of Dopamine dystonia |
Dopamine ![]() |
Iodosulpride |
Mouse knockout: Hyperactivity |
Dopamine ![]() |
Clozapine: High affinity | Autonomic hyperactivity |
Dopamine ![]() |
. | ? |
Vesicular amine ![]() (SLC18A1 ![]() |
Adrenal chromaffin granules | ? |
Vesicular amine ![]() (SLC18A2 ![]() |
Accumulates cytosolic monoamines into Brain synaptic vesicles |
Site of action of reserpine and tetrabenazine |
Aldehyde ![]() ![]() |
Dopamine inactivation with MAO |
?
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Neurofibromin
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Tumor suppressor | Pheochromocytoma
![]() Neurofibromatosis ![]() |
G7 protein
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Tumor suppressor | Pheochromocytoma
![]() Von Hippel-Lindau ![]() |
RET tyrosine-protein kinase receptor ![]() ![]() |
Oncogene
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Pheochromocytoma
![]() Multiple endocrine neoplasia 2 ![]() |
Transmitter metabolism | |||
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Precursors: | Tyrosine ® (a) L-dihydroxyphenylalanine (L-DOPA) (b) dopamine | ||
Synthesizing enzymes: |
(a) Tyrosine hydroxylase, (b) L-aromatic amino acid decarboxylase (DOPA decarboxylase) | ||
Metabolizing enzymes: | MAO and COMT | ||
Metabolites: | 3,4-Dihydroxyphenylacetic acid (DOPAC) Homovanillic acid (HVA) |
Dopamine Receptors | ||||
---|---|---|---|---|
Receptor subtypes |
Agonists | Antagonists | Second messenger | Disorders |
D1
![]() ![]() |
SKF 38393 Dihydrexiedine |
Sch 23390 SKF83566 SCH39166 |
Positive: cAMP G-protein Stimulate adenylyl cyclase |
Mouse knockout Hyperactivity Diastolic hypertension |
D2
![]() ![]() |
(+)PHNO Bromocriptine |
(s)-Sulpiride Raclopride Domperidone Haloperidol |
Positive: gK+ G-protein Inhibit adenylyl cyclase |
Myoclonus-Dystonia
![]() Anti-psychotic drugs |
D3
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7-OH-DPAT PD128907 BP897 |
Nafadotride | Positive: Ion channel | Mouse knockout Hyperactivity |
D4
![]() ![]() |
. | L745870 L741742 U101387 |
Positive: Ion channel | Autonomic dysfunction |
D5
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. | . | Positive: cAMP G-protein |
Focal dystonia Blepharospasm ![]() |
Transmitter Metabolism | |||
---|---|---|---|
Precursors: | L-Tyrosine (a) → L-DOPA (b) → Dopamine (c) → Noradrenaline (d) → Adrenaline | ||
Synthesizing enzymes: | (a) Tyrosine hydroxylase, (b) L-aromatic amino acid decarboxylase, (c) Dopamine ß-hydroxylase, (d) Phenylethanolamine-N-methyl transferase | ||
Metabolizing enzymes: | MAO and COMT | ||
Metabolites: | Vanillylmandelic acid (VMA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) |
Adrenoceptors | ||||
---|---|---|---|---|
Receptor subtypes | Transmitter | Agonists | Antagonists | Second messenger |
α(1A)
![]() α(1C) | NA > A | A61603 | KMD3213 (+)-niguldipine 5-methyluradipil |
Ca++: Influx into cell |
α(1B)
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NA = A | . | Spiroperone AH1111OA Chloroethylclonidine |
PI & Ca++; G-protein |
α(1D)
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NA = A | . | BMY7378 | PI & Ca++; G-protein |
α(2A)
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A > NA | Oxymetazoline | . | (-ve)cAMP, (down)gCa++, (down)gK+; G-protein |
α(2B)
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A > NA | . | Prazosin ARC 239 |
(-ve)cAMP, (down)gCa++; G-protein |
α(2C)
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A > NA | . | Prazosin ARC 239 |
(-ve)cAMP; G-protein |
β(1)
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NA > A | Xamoterol, RO363 |
Atenolol CGP20712A Betaxolol |
(+ve)cAMP; G-protein |
β(2)
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A > NA | Procaterol Zinterol |
ICI118551 | (+ve)cAMP; G-protein |
β(3)
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NA > A | BRL37344 | Bupranolol SR59230A |
(+ve)cAMP; G-protein |
NB: (+ve) indicates increase; (-ve) indicates decrease.