1B66

6-PYRUVOYL TETRAHYDROPTERIN SYNTHASE

1B66 の概要

• エントリーDOI: 10.2210/pdb1b66/pdb
• 分子名称: 6-PYRUVOYL TETRAHYDROPTERIN SYNTHASE, ZINC ION, BIOPTERIN, ... (4 entities in total)
• 機能のキーワード: tetrahydrobiopterin biosynthesis, phosphate elimination, pterine synthesis
• 由来する生物種: Rattus rattus (black rat)
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 32355.58

構造登録者

Ploom, T.,Thoeny, B.,Yim, J.,Lee, S.,Nar, H.,Leimbacher, W.,Huber, R.,Richardson, J.,Auerbach, G. (登録日: 1999-01-20, 公開日: 1999-04-27, 最終更新日: 2024-05-22)

主引用文献

Ploom, T.,Thony, B.,Yim, J.,Lee, S.,Nar, H.,Leimbacher, W.,Richardson, J.,Huber, R.,Auerbach, G.
Crystallographic and kinetic investigations on the mechanism of 6-pyruvoyl tetrahydropterin synthase.
J.Mol.Biol., 286:851-860, 1999

PubMed Abstract: The enzyme 6-pyruvoyl tetrahydropterin synthase (PTPS) catalyses the second step in the de novo biosynthesis of tetrahydrobiopterin, the conversion of dihydroneopterin triphosphate to 6-pyruvoyl tetrahydropterin. The Zn and Mg-dependent reaction includes a triphosphate elimination, a stereospecific reduction of the N5-C6 double bond and the oxidation of both side-chain hydroxyl groups. The crystal structure of the inactive mutant Cys42Ala of PTPS in complex with its natural substrate dihydroneopterinetriphosphate was determined at 1.9 A resolution. Additionally, the uncomplexed enzyme was refined to 2.0 A resolution. The active site of PTPS consists of the pterin-anchoring Glu A107 neighboured by two catalytic motifs: a Zn(II) binding site and an intersubunit catalytic triad formed by Cys A42, Asp B88 and His B89. In the free enzyme the Zn(II) is in tetravalent co-ordination with three histidine ligands and a water molecule. In the complex the water is replaced by the two substrate side-chain hydroxyl groups yielding a penta-co-ordinated Zn(II) ion. The Zn(II) ion plays a crucial role in catalysis. It activates the protons of the substrate, stabilizes the intermediates and disfavours the breaking of the C1'C2' bond in the pyruvoyl side-chain. Cys A42 is activated by His B89 and Asp B88 for proton abstraction from the two different substrate side-chain atoms C1', and C2'. Replacing Ala A42 in the mutant structure by the wild-type Cys by modelling shows that the C1' and C2' substrate side-chain protons are at equal distances to Cys A42 Sgamma. The basicity of Cys A42 may be increased by a catalytic triad His B89 and Asp B88. The active site of PTPS seems to be optimised to carry out proton abstractions from two different side-chain C1' and C2' atoms, with no obvious preference for one of them. Kinetic studies with dihydroneopterin monophosphate reveal that the triphosphate moiety of the substrate is necessary for enzyme specifity.

PubMed: 10024455
DOI: 10.1006/jmbi.1998.2511

実験手法

X-RAY DIFFRACTION (1.9 Å)