TPI Tutorial

TPI Tutorial - Triose Phosphate Isomerase Tutorial A....

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Triose Phosphate Isomerase Tutorial A. Structure This image shows the structure of triose phosphate isomerase (TPI), looking down at what would be the top of the barrel structure into the active site. This is a basic “ribbon” structure with -helix show in blue and - sheet in orange. Note the following: Lid Loop (amino acids 166- 176) Glutamic acid 165 Histidine 95 This side chains of Glu 165 and His 95 are shown as ball and stick structures, and the substrate is also shown in ball and stick form. The binding of substrate to the active site induces a conformational change in the structure of TPI, the induced fit , where the lid loop closes to trap the substrate in the active site. This has the effect of stabilizing the cis-enediol intermediate so that the activation energies for conversion of the substrate to enediol, and conversion of enediol to the product are decreased. Keep in mind that the reaction catalyzed by TPI is reversible, and occurs in both directions cells to either break down glucose for energy or make new glucose. The reaction mechanism is identical for conversion of G3P to DHAP and DHAP to G3P, but simply in reverse. It can be hard to get a good feel for what the structure of the active site really looks like, and how the lid loop compresses the substrate, from the above structure. You can get a much better picture of this by looking at a 3D-image that you can manipulate with a viewing program. The Protein Data Bank
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This note was uploaded on 09/20/2011 for the course BIBC 102 taught by Professor Price during the Summer '02 term at UCSD.

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TPI Tutorial - Triose Phosphate Isomerase Tutorial A....

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