1eun
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(New page: 200px<br /><applet load="1eun" size="450" color="white" frame="true" align="right" spinBox="true" caption="1eun, resolution 2.00Å" /> '''STRUCTURE OF 2-KETO-...)
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Revision as of 12:12, 20 November 2007
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STRUCTURE OF 2-KETO-3-DEOXY-6-PHOSPHOGLUCONATE ALDOLASE FROM ESCHERICHIA COLI
Overview
2-Keto-3-deoxy-6-phosphogluconate (KDPG) aldolase catalyzes the reversible, cleavage of KDPG to pyruvate and glyceraldehyde-3-phosphate. The enzyme is, a class I aldolase whose reaction mechanism involves formation of Schiff, base intermediates between Lys-133 and a keto substrate. A covalent adduct, was trapped by flash freezing KDPG aldolase crystals soaked with 10 mM, pyruvate in acidic conditions at pH 4.6. Structure determination to 1.95-A, resolution showed that pyruvate had undergone nucleophilic attack with, Lys-133, forming a protonated carbinolamine intermediate, a functional, Schiff base precursor, which was stabilized by hydrogen bonding with, active site residues. Carbinolamine interaction with Glu-45 indicates, general base catalysis of several rate steps. Stereospecific addition is, ensured by aromatic interaction of Phe-135 with the pyruvate methyl group., In the native structure, Lys-133 donates all of its hydrogen bonds, indicating the presence of an epsilon-ammonium salt group. Nucleophilic, activation is postulated to occur by proton transfer in the monoprotonated, zwitterionic pair (Glu-45/Lys-133). Formation of the zwitterionic pair, requires prior side chain rearrangement by protonated Lys-133 to displace, a water molecule, hydrogen bonded to the zwitterionic residues.
About this Structure
1EUN is a Single protein structure of sequence from Escherichia coli with SO4 as ligand. Active as 2-dehydro-3-deoxy-phosphogluconate aldolase, with EC number 4.1.2.14 Full crystallographic information is available from OCA.
Reference
Covalent intermediate trapped in 2-keto-3-deoxy-6- phosphogluconate (KDPG) aldolase structure at 1.95-A resolution., Allard J, Grochulski P, Sygusch J, Proc Natl Acad Sci U S A. 2001 Mar 27;98(7):3679-84. PMID:11274385
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