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Case Reports
. 1996 Jul;5(7):1023-8.
doi: 10.1093/hmg/5.7.1023.

Recessively inherited L-DOPA-responsive parkinsonism in infancy caused by a point mutation (L205P) in the tyrosine hydroxylase gene

B Lüdecke  1 , P M Knappskog, P T Clayton, R A Surtees, J D Clelland, S J Heales, M P Brand, K Bartholomé, T Flatmark
Affiliations
Case Reports

Recessively inherited L-DOPA-responsive parkinsonism in infancy caused by a point mutation (L205P) in the tyrosine hydroxylase gene

B Lüdecke et al. Hum Mol Genet. 1996 Jul.

Abstract

Tyrosine hydroxylase (TH) catalyzes the conversion of L-tyrosine to L-dihydroxyphenylalanine (L-DOPA), the rate-limiting step in the biosynthesis of dopamine. This report describes a missense point mutation in the human TH (hTH) gene in a girl presenting parkinsonian symptoms in early infancy and a very low level of the dopamine metabolite homovanillic acid in the CSF. DNA sequencing revealed a T614-to-C transition in exon 5 (L205P). Both parents and the patient's brother are heterozygous for the mutation. Site-directed mutagenesis and expression in different systems revealed that the recombinant mutant enzyme had a low homospecific activity, i.e. approximately 1.5% of wt-hTH in E. coli and approximately 16% in a cell-free in vitro transcription-translation system. When transiently expressed in human embryonic kidney (A293) cells a very low specific activity (approximately 0.3% of wt-hTH) and immunoreactive hTH (< 2%) was obtained. The expression studies are compatible with the severe clinical phenotype of the L205P homozygous patient carrying this recessively inherited mutation. Treatment with L-DOPA resulted in normalisation of the CSF homovanillic acid concentration and a sustained improvement in parkinsonian symptoms.

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