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 PubMedThe glycolytic enzyme triosephosphate isomerase (TIM) catalyzes the interconversion of the three-carbon sugars dihydroxyacetone phosphate (DHAP) and D-glyceraldehyde 3-phosphate (GAP) at a rate limited by the diffusion of substrate to the enzyme. We have solved the three-dimensional structure of TIM complexed with a reactive intermediate analogue, phosphoglycolohydroxamate (PGH), at 1.9-A resolution and have refined the structure to an R-factor of 18%. Analysis of the refined structure reveals the geometry of the active-site residues and the interactions they make with the inhibitor and, by analogy, the substrates. The structure is consistent with an acid-base mechanism in which the carboxylate of Glu-165 abstracts a proton from carbon while His-95 donates a proton to oxygen to form an enediol (or enediolate) intermediate. The conformation of the bound substrate stereoelectronically favors proton transfer from substrate carbon to the syn orbital of Glu-165. The crystal structure suggests that His-95 is neutral rather than cationic in the ground state and therefore would have to function as an imidazole acid instead of the usual imidazolium. Lys-12 is oriented so as to polarize the substrate oxygens by hydrogen bonding and/or electrostatic interaction, providing stabilization for the charged transition state. Asn-10 may play a similar role. Structure of the triosephosphate isomerase-phosphoglycolohydroxamate complex: an analogue of the intermediate on the reaction pathway.,Davenport RC, Bash PA, Seaton BA, Karplus M, Petsko GA, Ringe D Biochemistry. 1991 Jun 18;30(24):5821-6. PMID:2043623[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences | ||||||||||||||||||||
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