Impact of tumour necrosis factor-alpha and interferon-gamma on tetrahydrobiopterin synthesis in murine fibroblasts and macrophages.
Biochem J 1991;
280 ( Pt 3):709-14. [PMID:
1764035 PMCID:
PMC1130511 DOI:
10.1042/bj2800709]
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Abstract
Tumour necrosis factor-alpha causes an up to 30-fold induction of GTP cyclohydrolase I (EC 3.5.4.16) activity in murine dermal fibroblasts in a dose-dependent manner. Owing to the high constitutive activities of 6-pyruvoyltetrahydropterin synthase and sepiapterin reductase (EC 1.1.1.153), this potentiates biosynthesis of tetrahydrobiopterin. Murine macrophages already contain high activities of GTP cyclohydrolase I when unstimulated, and this is further augmented up to 4-fold by tumour necrosis factor-alpha/interferon-gamma. In Western blots an antiserum to murine liver GTP cyclohydrolase I does not stain cell extracts with high enzyme activities, suggesting that the cytokine induced peripheral form of GTP cyclohydrolase I might differ from the liver form.
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