Triosephosphate isomerase (TPI) is glycolytic enzyme essential for efficient energy production and are expressed in all prokaryotic and eukaryotic organisms. TPI and GAPDH have been considered to associate with brain microtubules. TPI1 is an enzyme, consisting of two identical proteins, which catalyzes the isomerization of glyceraldehydes 3-phosphate (G3P) and dihydroxy-acetone phosphate (DHAP) in glycolysis and gluconeogenesis. Mutations in TPI1 are associated with triosephosphate isomerase deficiency.