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SCHIFF BASE INTERMEDIATE IN KDPG ALDOLASE FROM ESCHERICHIA COLI
Structural highlights
FunctionEvolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed2-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. 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[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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