47. Conversion of Amino Acids to Specialized Products: Synthesis and Degradation of Catecholamines (Dopamine, Epinephrine and Norepinephrine). Pathobiochemistry of Parkinson's disease.
Covers the synthesis of catecholamines from tyrosine, giving each enzymatic step with its cofactor and noting the rate-limiting hydroxylation, then explains their degradation by MAO and COMT and the urinary end products VMA and HVA. Also outlines the pathobiochemistry of Parkinson's disease, including dopamine loss, the dopamine-acetylcholine imbalance, motor features and proposed causes, and closes with the biochemical rationale for levodopa, carbidopa and related drugs.
Topic 47 of 76 in the MU Pleven syllabus for Biochemistry (Medicine, Year 2). The free AceMed note covers it in 4 sections, about 279 words (2 min of reading), with 10 flashcards.
In this note
Conversion of Amino Acids to Specialized Products: Synthesis and Degradation of Catecholamines (Dopamine, Epinephrine and Norepinephrine).
Conversion of Amino Acids to Specialized Products
Pathobiochemistry of Parkinson’s Disease
Treatment Principles (Biochemical Rationale)
Conversion of Amino Acids to Specialized Products
Synthesis and Degradation of Catecholamines
Starting Amino Acid: Tyrosine (which itself is derived from Phenylalanine).
Catecholamine synthesis mainly occurs in:
Adrenal medulla
Postganglionic sympathetic neurons
CNS (substantia nigra and hypothalamus)
Steps in Catecholamine Synthesis (Enzymes + Cofactors)
Tyrosine → DOPA
Enzyme: Tyrosine Hydroxylase
Cofactor: Tetrahydrobiopterin (BH4)
Significance:Rate-limiting step.
DOPA → Dopamine
Enzyme: DOPA Decarboxylase
Cofactor: Vitamin B6 (Pyridoxal phosphate)
Dopamine → Norepinephrine
Enzyme: Dopamine β-Hydroxylase
Cofactor: Vitamin C
Occurs mainly inside synaptic vesicles and adrenal medulla.
