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| - | [[Image:1h6l.gif|left|200px]] | + | {{Seed}} |
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| | {{STRUCTURE_1h6l| PDB=1h6l | SCENE= }} | | {{STRUCTURE_1h6l| PDB=1h6l | SCENE= }} |
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| - | '''BETA-PROPELLER PHYTASE IN COMPLEX WITH PHOSPHATE AND CALCIUM IONS'''
| + | ===BETA-PROPELLER PHYTASE IN COMPLEX WITH PHOSPHATE AND CALCIUM IONS=== |
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| - | ==Overview==
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| - | BACKGROUND: Phytases hydrolyze phytic acid (myo-inositol-hexakisphosphate) to less-phosphorylated myo-inositol derivatives and inorganic phosphate. Phytases are used in animal feed to reduce phosphate pollution in the environment. Recently, a thermostable, calcium-dependent Bacillus phytase was identified that represents the first example of the beta propeller fold exhibiting phosphatase activity. We sought to delineate the catalytic mechanism and property of this enzyme. RESULTS: The crystal structure of the enzyme in complex with inorganic phosphate reveals that two phosphates and four calcium ions are tightly bound at the active site. Mutation of the residues involved in the calcium chelation results in severe defects in the enzyme's activity. One phosphate ion, chelating all of the four calcium ions, is close to a water molecule bridging two of the bound calcium ions. Fluoride ion, which is expected to replace this water molecule, is an uncompetitive inhibitor of the enzyme. The enzyme is able to hydrolyze any of the six phosphate groups of phytate. CONCLUSIONS: The enzyme reaction is likely to proceed through a direct attack of the metal-bridging water molecule on the phosphorous atom of a substrate and the subsequent stabilization of the pentavalent transition state by the bound calcium ions. The enzyme has two phosphate binding sites, the "cleavage site", which is responsible for the hydrolysis of a substrate, and the "affinity site", which increases the binding affinity for substrates containing adjacent phosphate groups. The existence of the two nonequivalent phosphate binding sites explains the puzzling formation of the alternately dephosphorylated myo-inositol triphosphates from phytate and the hydrolysis of myo-inositol monophosphates.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_11566134}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 11566134 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_11566134}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Phytase]] | | [[Category: Phytase]] |
| | [[Category: Propeller]] | | [[Category: Propeller]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 18:29:58 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 06:42:38 2008'' |
Revision as of 03:42, 1 July 2008
Template:STRUCTURE 1h6l
BETA-PROPELLER PHYTASE IN COMPLEX WITH PHOSPHATE AND CALCIUM IONS
Template:ABSTRACT PUBMED 11566134
About this Structure
1H6L is a Single protein structure of sequence from Bacillus amyloliquefaciens. Full crystallographic information is available from OCA.
Reference
Enzyme mechanism and catalytic property of beta propeller phytase., Shin S, Ha NC, Oh BC, Oh TK, Oh BH, Structure. 2001 Sep;9(9):851-8. PMID:11566134
Page seeded by OCA on Tue Jul 1 06:42:38 2008
