Location of the active site and proposed catalytic mechanism of 
pterin-4a-carbinolamine dehydratase

Köster, Sandra; Stier, Gunter; Ficner, Ralf; Hölzer, Manuela; Curtius, Hans−Christoph; Suck, Dietrich; Ghisla, Sandro

doi:10.1111/j.1432-1033.1996.00858.x

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Location of the active site and proposed catalytic mechanism of pterin-4a-carbinolamine dehydratase

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Stier, Gunter
Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Max Planck Society;

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Citation

Köster, S., Stier, G., Ficner, R., Hölzer, M., Curtius, H., Suck, D., et al. (1996). Location of the active site and proposed catalytic mechanism of pterin-4a-carbinolamine dehydratase. European Journal of Biochemistry, 241(3), 858-864. doi:10.1111/j.1432-1033.1996.00858.x.

Cite as: https://hdl.handle.net/11858/00-001M-0000-0019-A681-7

Abstract

Based on the recently solved three-dimensional structure of pterin-4a-carbinolamine dehydratase from rat/human liver the involvement of the proposed active-site residues Glu57, Asp60, His61, His62, Tyr69, His79, Arg87 and Asp88 was examined by site-directed mutagenesis. Most of the mutants showed reduced activity, and only the Glu57→Ala mutant and the His61→Ala, His62→Ala double mutant were fully devoid of activity. The dissociation constants of quinonoid 6,6-dimethyl-7,8-dihydropterin were significantly increased for binding to the Glu57→Ala, His61→Ala, His62→Ala single mutants and the His61→Ala, His62→Ala double mutant, confirming that His61 and His62 are essential for substrate binding and catalysis. The mechanism of dehydration is proposed to involve base catalysis at the N(5)-H group of the substrate by His61.