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Phosphate ions in D33S mutant fructose-1,6-bisphosphate aldolase from rabbit musclePhosphate ions in D33S mutant fructose-1,6-bisphosphate aldolase from rabbit muscle
Structural highlights
Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedFructose-1,6-bisphosphate muscle aldolase is an essential glycolytic enzyme that catalyzes reversible carbon-carbon bond formation by cleaving fructose 1,6-bisphosphate to yield dihydroxyacetone phosphate (DHAP) and d-glyceraldehyde phosphate. To elucidate the mechanistic role of conserved amino acid Asp-33, Asn-33 and Ser-33 mutants were examined by kinetic and structural analyses. The mutations significantly compromised enzymatic activity and carbanion oxidation in presence of DHAP. Detailed structural analysis demonstrated that, like native crystals, Asp-33 mutant crystals, soaked in DHAP solutions, trapped Schiff base-derived intermediates covalently attached to Lys-229. The mutant structures, however, exhibited an abridged conformational change with the helical region (34-65) flanking the active site as well as pK(a) reductions and increased side chain disorder by central lysine residues, Lys-107 and Lys-146. These changes directly affect their interaction with the C-terminal Tyr-363, consistent with the absence of active site binding by the C-terminal region in the presence of phosphate. Lys-146 pK(a) reduction and side chain disorder would further compromise charge stabilization during C-C bond cleavage and proton transfer during enamine formation. These mechanistic impediments explain diminished catalytic activity and a reduced level of carbanion oxidation and are consistent with rate-determining proton transfer observed in the Asn-33 mutant. Asp-33 reduces the entropic cost and augments the enthalpic gain during catalysis by rigidifying Lys-107 and Lys-146, stabilizing their protonated forms, and promoting a conformational change triggered by substrate or obligate product binding, which lower kinetic barriers in C-C bond cleavage and Schiff base-enamine interconversion. Charge Stabilization and Entropy Reduction of Central Lysine Residues in Fructose-Bisphosphate Aldolase.,St-Jean M, Blonski C, Sygusch J Biochemistry. 2009 Apr 22. PMID:19354220[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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