3b8d: Difference between revisions
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==Overview== | ==Overview== | ||
The aldolase catalytic cycle consists of a number of proton transfers that | The aldolase catalytic cycle consists of a number of proton transfers that interconvert covalent enzyme intermediates. Glu-187 is a conserved amino acid that is located in the mammalian fructose-1,6-bisphosphate aldolase active site. Its central location, within hydrogen bonding distance of three other conserved active site residues: Lys-146, Glu-189, and Schiff base-forming Lys-229, makes it an ideal candidate for mediating proton transfers. Point mutations, Glu-187--> Gln, Ala, which would inhibit proton transfers significantly, compromise activity. Trapping of enzymatic intermediates in Glu-187 mutants defines a proton transfer role for Glu-187 in substrate cleavage and Schiff base formation. Structural data show that loss of Glu-187 negative charge results in hydrogen bond formation between Lys-146 and Lys-229 consistent with a basic pK(a) for Lys-229 in native enzyme and supporting nucleophilic activation of Lys-229 by Glu-187 during Schiff base formation. The crystal structures also substantiate Glu-187 and Glu-189 as present in ionized form in native enzyme, compatible with their role of catalyzing proton exchange with solvent as indicated from solvent isotope effects. The proton exchange mechanism ensures Glu-187 basicity throughout the catalytic cycle requisite for mediating proton transfer and electrostatic stabilization of ketamine intermediates. Glutamate general base catalysis is a recurrent evolutionary feature of Schiff base0forming aldolases. | ||
==About this Structure== | ==About this Structure== | ||
3B8D is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Oryctolagus_cuniculus Oryctolagus cuniculus] with <scene name='pdbligand=SO4:'>SO4</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. This structure | 3B8D is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Oryctolagus_cuniculus Oryctolagus cuniculus] with <scene name='pdbligand=SO4:'>SO4</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. This structure supersedes the now removed PDB entry 1EWG. Active as [http://en.wikipedia.org/wiki/Fructose-bisphosphate_aldolase Fructose-bisphosphate aldolase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.1.2.13 4.1.2.13] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3B8D OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: schiff base]] | [[Category: schiff base]] | ||
''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 19:04:04 2008'' | ||
Revision as of 20:04, 21 February 2008
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Fructose 1,6-bisphosphate aldolase from rabbit muscle
OverviewOverview
The aldolase catalytic cycle consists of a number of proton transfers that interconvert covalent enzyme intermediates. Glu-187 is a conserved amino acid that is located in the mammalian fructose-1,6-bisphosphate aldolase active site. Its central location, within hydrogen bonding distance of three other conserved active site residues: Lys-146, Glu-189, and Schiff base-forming Lys-229, makes it an ideal candidate for mediating proton transfers. Point mutations, Glu-187--> Gln, Ala, which would inhibit proton transfers significantly, compromise activity. Trapping of enzymatic intermediates in Glu-187 mutants defines a proton transfer role for Glu-187 in substrate cleavage and Schiff base formation. Structural data show that loss of Glu-187 negative charge results in hydrogen bond formation between Lys-146 and Lys-229 consistent with a basic pK(a) for Lys-229 in native enzyme and supporting nucleophilic activation of Lys-229 by Glu-187 during Schiff base formation. The crystal structures also substantiate Glu-187 and Glu-189 as present in ionized form in native enzyme, compatible with their role of catalyzing proton exchange with solvent as indicated from solvent isotope effects. The proton exchange mechanism ensures Glu-187 basicity throughout the catalytic cycle requisite for mediating proton transfer and electrostatic stabilization of ketamine intermediates. Glutamate general base catalysis is a recurrent evolutionary feature of Schiff base0forming aldolases.
About this StructureAbout this Structure
3B8D is a Single protein structure of sequence from Oryctolagus cuniculus with as ligand. This structure supersedes the now removed PDB entry 1EWG. Active as Fructose-bisphosphate aldolase, with EC number 4.1.2.13 Full crystallographic information is available from OCA.
ReferenceReference
A conserved glutamate residue exhibits multifunctional catalytic roles in D-fructose-1,6-bisphosphate aldolases., Maurady A, Zdanov A, de Moissac D, Beaudry D, Sygusch J, J Biol Chem. 2002 Mar 15;277(11):9474-83. Epub 2002 Jan 4. PMID:11779856
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