4a-hydroxytetrahydrobiopterin dehydratase

Thus, the two substrates of this enzyme are (6R)-6-(L-erythro-1,2-dihydroxypropyl)-5,6,7,8-tetrahydro-4a- and hydroxypterin, whereas its two products are (6R)-6-(L-erythro-1,2-dihydroxypropyl)-7,8-dihydro-6H-pterin and H₂O.

This enzyme belongs to the family of lyases, specifically the hydro-lyases, which cleave carbon-oxygen bonds. The systematic name of this enzyme class is (6R)-6-(L-erythro-1,2-dihydroxypropyl)-5,6,7,8-tetrahydro-4a-hydroxy pterin hydro-lyase [(6R)-6-(L-erythro-1,2-dihydroxypropyl)-7,8-dihydro-6H-pterin-formin g]. Other names in common use include 4alpha-hydroxy-tetrahydropterin dehydratase, pterin-4alpha-carbinolamine dehydratase, and 4a-hydroxytetrahydrobiopterin hydro-lyase.

Structural studies

As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes 1DCO, 1DCP, and 1RU0.

References

Blau N, Ghisla S, Heizmann CW (1993). "Phenylalanine hydroxylase-stimulating protein/pterin-4 alpha-carbinolamine dehydratase from rat and human liver Purification, characterization, and complete amino acid sequence". J. Biol. Chem. 268 (7): 4828–31. PMID 8444860.

Carbon-oxygen lyases (EC 4.2) (primarily dehydratases)

4.2.1: Hydro-Lyases	Carbonic anhydrase Fumarase Aconitase Enolase Alpha Enolase 2 Enoyl-CoA hydratase/3-Hydroxyacyl ACP dehydrase Methylglutaconyl-CoA hydratase Tryptophan synthase Cystathionine beta synthase Porphobilinogen synthase 3-Isopropylmalate dehydratase Urocanase Uroporphyrinogen III synthase Nitrile hydratase

4.2.2: Acting on polysaccharides	Hyaluronate lyase

4.2.3: Acting on phosphates	Threonine synthase

4.2.99: Other	Carboxymethyloxysuccinate lyase

Enzymes

Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Catalytically perfect enzyme Coenzyme Cofactor Enzyme catalysis Enzyme kinetics Lineweaver–Burk plot Michaelis–Menten kinetics

Regulation	Allosteric regulation Cooperativity Enzyme inhibitor

Classification	EC number Enzyme superfamily Enzyme family List of enzymes

Types	EC1 Oxidoreductases(list) EC2 Transferases(list) EC3 Hydrolases(list) EC4 Lyases(list) EC5 Isomerases(list) EC6 Ligases(list)

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