Скачать или смотреть 16. Special Products from Amino Acids | Catecholamines (Dopamine, Norepinephrine, Epinephrine) USMLE

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Special Products from Amino Acids | Catecholamines (Dopamine, Norepinephrine, Epinephrine) | MBBS Biochemistry | USMLE Step 1

👋 Hey future doctors and biochem enthusiasts! Did you know that the fight-or-flight hormones — dopamine, norepinephrine, and epinephrine — all come from a single amino acid: Tyrosine? ⚡ These catecholamines are central to stress response, autonomic regulation, and brain neurotransmission, making them must-know derivatives of amino acids for your exams.

This lecture explains the biosynthesis, regulation, and clinical relevance of catecholamines, integrating biochemistry with physiology and pathology. Perfect for MBBS, NEET PG, FMGE, and USMLE Step 1 preparation. 🧬📚

🌟 Catecholamine Pathway

1️⃣ Tyrosine → L-DOPA

Enzyme: Tyrosine hydroxylase (rate-limiting, requires BH₄ cofactor).

2️⃣ L-DOPA → Dopamine

Enzyme: DOPA decarboxylase (requires pyridoxal phosphate, Vitamin B6).

Dopamine = neurotransmitter in CNS reward, movement, and mood regulation.

3️⃣ Dopamine → Norepinephrine

Enzyme: Dopamine β-hydroxylase (requires Vitamin C, Cu²⁺).

Norepinephrine = major sympathetic neurotransmitter.

4️⃣ Norepinephrine → Epinephrine

Enzyme: Phenylethanolamine N-methyltransferase (PNMT) (stimulated by cortisol).

Epinephrine = adrenal medulla hormone, mediates stress, glucose mobilization, cardiac stimulation.

🩺 Clinical Correlations

Parkinson’s disease: dopamine deficiency in substantia nigra.

Schizophrenia & Psychosis: altered dopamine pathways.

Pheochromocytoma: tumor of adrenal medulla → excess catecholamines → hypertension, palpitations, sweating.

Neuroblastoma: childhood tumor producing catecholamines.

MAOI + Tyramine (“cheese reaction”): hypertensive crisis from excessive norepinephrine release.

Drugs:
• L-DOPA for Parkinson’s.
• Reserpine inhibits storage of catecholamines.
• Cocaine & amphetamines ↑ synaptic catecholamines.

🎯 Exam Integration

Tyrosine is the precursor of catecholamines.

Tyrosine hydroxylase = rate-limiting enzyme.

Cofactors: BH₄ (hydroxylase), B6 (decarboxylase), Vitamin C/Cu (hydroxylase), SAM (PNMT).
👉 Favorite topic for USMLE Step 1 and NEET PG case-based MCQs.

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❓Got requests for related topics like serotonin, melatonin, or histamine? Drop them in the comments below — we’d love to cover them in detail! 😊

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