Triose Phosphate Isomerase: Difference between revisions

'''Triose Phosphate Isomerase''' (TPI or TIM) [5.3.1.1] is a ubiquitous enzyme with a molecular weight of roughly 54 kD (27 kD per subunit) which catalyzes the reversible interconversion of the triose phosphate isomers dihydroxyacetone phosphate ([http://en.wikipedia.org/wiki/DHAP DHAP]) and D-glyceraldehyde-3-phosphate <scene name='Triose_Phosphate_Isomerase/Pga/1'>(GAP)</scene>, an essential process in the glycolytic pathway. More simply, the enzyme catalyzes the [http://en.wikipedia.org/wiki/Isomerization isomerization] of a ketose (DHAP) to an aldose [http://en.wikipedia.org/wiki/Glyceraldehyde_3-phosphate GAP] also referred to as PGAL. In regards to the two isomers, at equilibrium, roughly 96% of the triose phosphate is in the DHAP isomer form; however, the isomerization reaction proceeds due to the rapid removal of GAP from the subsequent reactions of [http://en.wikipedia.org/wiki/Glycolysis glycolysis]. TPI is an example of a [http://en.wikipedia.org/wiki/Catalytically_perfect_enzyme catalytically perfect enzyme], indicating that for almost every enzyme-substrate encounter, a product is formed and that this interaction is only limited by the substrate diffusion rate. Diffusion as the rate limiting step was experimentally confirmed through the use of viscogens such as glycerol and sucrose. Other catalytically perfect enzymes include [http://en.wikipedia.org/wiki/Carbonic_anhydrase carbonic anhydrase], [http://en.wikipedia.org/wiki/Acetylcholinesterase acetylcholinesterase], [http://en.wikipedia.org/wiki/Catalase catalase] and [http://en.wikipedia.org/wiki/Fumarase fumarase]. In addition to its relevance in glycolysis, TPI is also involved in several additional metabolic biological processes including gluconeogenesis, the pentose phosphate shunt and fatty acid biosynthesis.