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Gütlich, M. ; Jäger, E. ; Rücknagel, K.P. ; Werner, T. ; Rödl, W. ; Ziegler, I. ; Bacher, A.

Human GTP cyclohydrolase I: Only one out of three cDNA isoforms gives rise to the active enzyme.

Biochem. J. 302, 215-221 (1994)
Open Access Green as soon as Postprint is submitted to ZB.
GTP cyclohydrolase I catalyses the first and rate-limiting step of tetrahydrobiopterin biosynthesis. Its expression is regulated by interferon-γ or kit ligand in a tissue-specific manner. Three different cDNA forms have been reported for human GTP cyclohydrolase I. We have isolated, from a human liver cDNA library, two clones which contained inserts identical with two of the cDNAs reported by Togari et al. The three open reading frames corresponding to all reported cDNA sequences were expressed in Escherichia coli. Only the recombinant protein corresponding to the longest reading frame catalysed the conversion of GTP into dihydroneopterin triphosphate. The proteins corresponding to the shorter reading frames failed to catalyse not only the generation of dihydroneopterin triphosphate but also the release of formate from GTP, an intermediate step of the reaction. Recombinant human GTP cyclohydrolase I showed sigmoidal substrate kinetics and maximum activity at 60°C. These findings are well in line with the published properties of the enzyme isolated from rat liver. The data indicate that cytokine-mediated induction of GTP cyclohydrolase I is not due to the expression of enzyme isoforms.
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Publication type Article: Journal article
Document type Scientific Article
Corresponding Author
ISSN (print) / ISBN 0264-6021
e-ISSN 1470-8728
Journal Biochemical Journal / Reviews
Quellenangaben Volume: 302, Issue: 1, Pages: 215-221 Article Number: , Supplement: ,
Publisher Portland Press
Non-patent literature Publications
Reviewing status Peer reviewed
Institute(s) Institute of Clinical Molecular Biology and Tumor Genetics (K.MOLBI)