Isomerases are a broad class of enzymes which catalyze structural change in a single molecule in biological systems. These structural changes can be extremely various, from very simple modifications such as the reorientation from levo to dextro alignment in the following amino acid:
COO- alanine COO-
| racemase |
H3N+--C--H ------> H--C--N+H3
| |
CH3 CH3
L-alanine D-alanine
Up to the fantastically complex
topology topological modifications in
DNA Topoisomerases, which uncoil and recoil long strands of
DNA to allow reading and copying.