Human Photoreactivating Enzyme: Action Spectrum and Safelight Conditions

Abstract

The photoreactivating enzyme (PRE) repairs UV-damaged DNA in a two-step reaction: the enzyme binds to a damaged region of the DNA containing a pyrimidine dimer, the enzyme-DNA complex absorbs a photon in the wavelength range 300–600 nm, resulting in photolysis of the dimer to constituent monomers and restoration of biological activity of the DNA (1,2,3). Although the photoreactivating enzyme was known to be widely distributed through both plant and animal kingdoms, most studies indicated that the enzyme was absent in placental mammals (4). Recent evidence indicates, however, that placental mammals do possess photoreactivating enzyme activity, that this activity can monomerize pyrimidine dimers in cellular DNA, and thus prevent UV-induced biological damage (5,6,7). I shall discuss these data with emphasis on the human enzyme, its deficiency in some human cells, and the possible role of the enzyme in DNA repair in man.