 The active site is found in each subunit between the two distinct α/β/α globular domains, the substrate binding domain and the coenzyme binding domain.This coenzyme binding domain is slightly larger than the substrate binding domain and contains a NAD(P) Rossmann fold along with the ""dimerisation loop"" which holds the two subunits of the homodimer together.In addition to linking the two proteins together, the ""dimerisation loop"" of each subunit protrudes into the active site of the other subunit increasing the specificity of the enzyme, by preventing the binding of pyruvate as a substrate.