Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.14.16.2 (tyrosine hydroxylase)
 14,760 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In cultured cells of the Bomirski Ab amelanotic hamster melanoma line, the substrates of tyrosinase, L-tyrosine, and L-DOPA induce the melanogenic pathway. In this report, we demonstrate that these substrates regulate the subcellular apparatus involved in their own metabolism and that this regulation is under the dynamic control of one of the components of this apparatus, tyrosinase, via tyrosine hydroxylase activity. Culturing cells with nontoxic but melanogenically inhibitory levels of phenylthiourea (PTU; 100 microM) strongly inhibits induction of both the tyrosine hydroxylase and DOPA oxidase activities of tyrosinase by L-tyrosine (200 microM) but has no effect on the induction of either activity by L-DOPA (50 microM). De novo synthesis of premelanosomes precedes the onset of tyrosine-induced melanogenesis. Thereafter, increases in the population of melanosomes (likewise inhibited by PTU) correlate positively with increases in tyrosinase activity induced by L-tyrosine. Melanogenesis induced by L-DOPA in the absence of L-tyrosine is rate-limited not by tyrosinase but by inadequate melanosome synthesis. Our findings indicate that in Bomirski Ab amelanotic hamster melanoma cells the synthesis of the subcellular apparatus of melanogenesis is initiated by L-tyrosine and is regulated further by tyrosinase and L-DOPA, which serves as a second messenger subsequent to tyrosine hydroxylase activity.
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PMID:L-tyrosine, L-dopa, and tyrosinase as positive regulators of the subcellular apparatus of melanogenesis in Bomirski Ab amelanotic melanoma cells. 249 48

We investigated the effect of hyper- and hypothyroidism on tyrosine hydroxylase protein concentration in the locus coeruleus (divided into anterior and posterior parts), the substantia nigra and the adrenals of adult rats. Rats were made hypothyroid with propylthiouracile (PTU, 0.02% in drinking water for 21 days) or hyperthyroid by thyroxine injection (100 or 250 micrograms/kg/day), for 3 or 17 days. PTU treatment resulted in statistically significant decrease of tyrosine hydroxylase in the anterior locus coeruleus (-13%) and the adrenals (-14%). After thyroxine treatment, in the anterior locus coeruleus, tyrosine hydroxylase was significantly higher (2 way ANOVA) after the 3 day treatment than after the 17 day treatment: tyrosine hydroxylase showed a trend to increase the 3 day treatment (+20% with the 250 micrograms/kg dose) and to decrease after the 17 day treatment (-15% with the 250 micrograms/kg dose). In the adrenals, tyrosine hydroxylase was increased by the 3 day treatment (+42% after the 250 micrograms/kg dose), but this increase was not observed after 17 days of treatment. Tyrosine hydroxylase was not altered in the posterior locus coeruleus and the substantia nigra, whatever the treatment. Together, our results support the hypothesis that in the anterior locus coeruleus and in the adrenals tyrosine hydroxylase level is positively modulated by thyroid hormones. After long-term treatment (17 days) this effect is not observed.
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PMID:Influence of the thyroid hormone status on tyrosine hydroxylase in central and peripheral catecholaminergic structures. 881 45