A DNA repair enzyme which recognizes and removes dimers that have formed between pyrimidine nitrogenous bases on the same strand as each other, as a result of too much ultraviolet radiation. The enzyme can only do this if visible light is present. It is also called a photoreactivating enzyme.

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.