Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0030567 (Parkinson's disease)
 63,064 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tetrahydrobiopterin (BH(4)) cofactor is essential for various processes, and is present in probably every cell or tissue of higher organisms. BH(4) is required for various enzyme activities, and for less defined functions at the cellular level. The pathway for the de novo biosynthesis of BH(4) from GTP involves GTP cyclohydrolase I, 6-pyruvoyl-tetrahydropterin synthase and sepiapterin reductase. Cofactor regeneration requires pterin-4a-carbinolamine dehydratase and dihydropteridine reductase. Based on gene cloning, recombinant expression, mutagenesis studies, structural analysis of crystals and NMR studies, reaction mechanisms for the biosynthetic and recycling enzymes were proposed. With regard to the regulation of cofactor biosynthesis, the major controlling point is GTP cyclohydrolase I, the expression of which may be under the control of cytokine induction. In the liver at least, activity is inhibited by BH(4), but stimulated by phenylalanine through the GTP cyclohydrolase I feedback regulatory protein. The enzymes that depend on BH(4) are the phenylalanine, tyrosine and tryptophan hydroxylases, the latter two being the rate-limiting enzymes for catecholamine and 5-hydroxytryptamine (serotonin) biosynthesis, all NO synthase isoforms and the glyceryl-ether mono-oxygenase. On a cellular level, BH(4) has been found to be a growth or proliferation factor for Crithidia fasciculata, haemopoietic cells and various mammalian cell lines. In the nervous system, BH(4) is a self-protecting factor for NO, or a general neuroprotecting factor via the NO synthase pathway, and has neurotransmitter-releasing function. With regard to human disease, BH(4) deficiency due to autosomal recessive mutations in all enzymes (except sepiapterin reductase) have been described as a cause of hyperphenylalaninaemia. Furthermore, several neurological diseases, including Dopa-responsive dystonia, but also Alzheimer's disease, Parkinson's disease, autism and depression, have been suggested to be a consequence of restricted cofactor availability.
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PMID:Tetrahydrobiopterin biosynthesis, regeneration and functions. 1072 95

Dopa-responsive dystonia (DRD) is a hereditary dystonia characterized by a childhood onset of fixed dystonic posture with a dramatic and sustained response to relatively low doses of levodopa. DRD is thought to result from striatal dopamine deficiency due to a reduced synthesis and activity of tyrosine hydroxylase (TH), the synthetic enzyme for dopamine. The mechanisms underlying the genesis of dystonia in DRD present a challenge to models of basal ganglia movement control, given that striatal dopamine deficiency is the hallmark of Parkinson's disease. We report here behavioral and anatomical observations on a transgenic mouse model for DRD in which the gene for 6-pyruvoyl-tetrahydropterin synthase is targeted to render selective dysfunction of TH synthesis in the striatum. Mutant mice exhibited motor deficits phenotypically resembling symptoms of human DRD and manifested a major depletion of TH labeling in the striatum, with a marked posterior-to-anterior gradient resulting in near total loss caudally. Strikingly, within the regions of remaining TH staining in the striatum, there was a greater loss of TH labeling in striosomes than in the surrounding matrix. The predominant loss of TH expression in striosomes occurred during the early postnatal period, when motor symptoms first appeared. We suggest that the differential striosome-matrix pattern of dopamine loss could be a key to identifying the mechanisms underlying the genesis of dystonia in DRD.
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PMID:Differential involvement of striosome and matrix dopamine systems in a transgenic model of dopa-responsive dystonia. 1871 55