Triose-phosphate isomerase (TIM), is an enzyme () that catalyzes the reversible interconvertion of triose phosphates isomers dihydroxyacetone phosphate and D-glyceraldehyde 3-phosphate.

TIM plays an important role in glycolysis and is essential for efficient energy production. TIM is found in all organisms in which it was looked for, including humans, chickens, the parasitic protozoan that causes sleeping sickness, and the intestinal bacterium E. coli.

Deficiencies in TIM are associated with haemolytic anaemia coupled with a progressive, severe neurological disorder.

Structure

---

TIM is a dimer of identical subunits, each of which is made up of about 250 amino acid residues. The three-dimensional structure of a subunit contains eight α-helices (blue and red) on the outside and eight parallel β-strands on the inside (violet and yellow). This structural motif is called an αβ-barrel, or a TIM-barrel, and is by far the most commonly observed protein fold. The active site of this enzyme is in the center of the barrel. A glutamic acid residue is involved in the catalytic mechanism. The sequence around the active site residue is conserved in all known TIM's.

See also

---

• TIM barrel

EC 5.3.1