1cjx
From Proteopedia
| Line 4: | Line 4: | ||
==Overview== | ==Overview== | ||
| - | BACKGROUND: In plants and photosynthetic bacteria, the tyrosine | + | BACKGROUND: In plants and photosynthetic bacteria, the tyrosine degradation pathway is crucial because homogentisate, a tyrosine degradation product, is a precursor for the biosynthesis of photosynthetic pigments, such as quinones or tocophenols. Homogentisate biosynthesis includes a decarboxylation step, a dioxygenation and a rearrangement of the pyruvate sidechain. This complex reaction is carried out by a single enzyme, the 4-hydroxyphenylpyruvate dioxygenase (HPPD), a non-heme iron dependent enzyme that is active as a homotetramer in bacteria and as a homodimer in plants. Moreover, in humans, a HPPD deficiency is found to be related to tyrosinemia, a rare hereditary disorder of tyrosine catabolism. RESULTS: We report here the crystal structure of Pseudomonas fluorescens HPPD refined to 2.4 A resolution (Rfree 27.6%; R factor 21.9%). The general topology of the protein comprises two barrel-shaped domains and is similar to the structures of Pseudomonas 2,3-dihydroxybiphenyl dioxygenase (DHBD) and Pseudomonas putida catechol 2,3-dioxygenase (MPC). Each structural domain contains two repeated betaalpha betabeta betaalpha modules. There is one non-heme iron atom per monomer liganded to the sidechains of His161, His240, Glu322 and one acetate molecule. CONCLUSIONS: The analysis of the HPPD structure and its superposition with the structures of DHBD and MPC highlight some important differences in the active sites of these enzymes. These comparisons also suggest that the pyruvate part of the HPPD substrate (4-hydroxyphenylpyruvate) and the O2 molecule would occupy the three free coordination sites of the catalytic iron atom. This substrate-enzyme model will aid the design of new inhibitors of the homogentisate biosynthesis reaction. |
==About this Structure== | ==About this Structure== | ||
| Line 28: | Line 28: | ||
[[Category: oxidoreductase]] | [[Category: oxidoreductase]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:06:48 2008'' |
Revision as of 10:06, 21 February 2008
|
CRYSTAL STRUCTURE OF PSEUDOMONAS FLUORESCENS HPPD
Overview
BACKGROUND: In plants and photosynthetic bacteria, the tyrosine degradation pathway is crucial because homogentisate, a tyrosine degradation product, is a precursor for the biosynthesis of photosynthetic pigments, such as quinones or tocophenols. Homogentisate biosynthesis includes a decarboxylation step, a dioxygenation and a rearrangement of the pyruvate sidechain. This complex reaction is carried out by a single enzyme, the 4-hydroxyphenylpyruvate dioxygenase (HPPD), a non-heme iron dependent enzyme that is active as a homotetramer in bacteria and as a homodimer in plants. Moreover, in humans, a HPPD deficiency is found to be related to tyrosinemia, a rare hereditary disorder of tyrosine catabolism. RESULTS: We report here the crystal structure of Pseudomonas fluorescens HPPD refined to 2.4 A resolution (Rfree 27.6%; R factor 21.9%). The general topology of the protein comprises two barrel-shaped domains and is similar to the structures of Pseudomonas 2,3-dihydroxybiphenyl dioxygenase (DHBD) and Pseudomonas putida catechol 2,3-dioxygenase (MPC). Each structural domain contains two repeated betaalpha betabeta betaalpha modules. There is one non-heme iron atom per monomer liganded to the sidechains of His161, His240, Glu322 and one acetate molecule. CONCLUSIONS: The analysis of the HPPD structure and its superposition with the structures of DHBD and MPC highlight some important differences in the active sites of these enzymes. These comparisons also suggest that the pyruvate part of the HPPD substrate (4-hydroxyphenylpyruvate) and the O2 molecule would occupy the three free coordination sites of the catalytic iron atom. This substrate-enzyme model will aid the design of new inhibitors of the homogentisate biosynthesis reaction.
About this Structure
1CJX is a Single protein structure of sequence from Pseudomonas fluorescens with , and as ligands. Active as 4-hydroxyphenylpyruvate dioxygenase, with EC number 1.13.11.27 Known structural/functional Sites: , , and . Full crystallographic information is available from OCA.
Reference
Crystal structure of Pseudomonas fluorescens 4-hydroxyphenylpyruvate dioxygenase: an enzyme involved in the tyrosine degradation pathway., Serre L, Sailland A, Sy D, Boudec P, Rolland A, Pebay-Peyroula E, Cohen-Addad C, Structure. 1999 Aug 15;7(8):977-88. PMID:10467142
Page seeded by OCA on Thu Feb 21 12:06:48 2008
