Which enzyme is deficient in Parkinsonism?
High-Yield Explanation
ANSWER: (C) Tyrosine hydroxylaseREF: Clinical Neurology for Psychiatrists 6th ed by David Myland Kaufman page 409 Pathophysiology of Parkinsonism:* The motor symptoms of Parkinson's disease result from the death of dopamine generating cells in the substantia nigra, a region of the midbrain.* The pathology of the disease is characterized by the accumulation of a protein called alpha synuclein into inclusions called Lewy bodies in neurons, and from insufficient formation and activity of dopamine produced in certain neurons within parts of the midbrainDOPAMINE SYNTHESISPhenylalaninePhenylalanine hydroxylase-----------------------TyrosineTyrosineTyrosine hydroxylase*-----------------------DOPADOPADOPA decarboxylase-----------------------DopamineThe presynaptic nigrostraital tract neurons normally converts phenylalanine to dopamine. In Parkinsons disease however the nigrostraital neurons slowly degenerate and looses their Tyrosine hydroxylase.The loss of tyrosine hydroxylase represents the critical failure in Parkinsons disease because this enzyme is the rate limiting enzyme in dopamine synthesis