Any Process That Results in a Change in State or Activity of a Cell (in Terms of Movement Secretion Enzyme Production Gene Expression Etc.) As a Result of a Stimulus Indicating Damage to Its DNA From Environmental Insults or Errors During Metabolism.
Catalysis of the Cleavage of C C C O C N and Other Bonds by Other Means Than by Hydrolysis or Oxidation or Conversely Adding a Group to a Double Bond. They Differ From Other Enzymes in That Two Substrates Are Involved in One Reaction Direction But Only One in the Other Direction. When Acting On the Single Substrate a Molecule Is Eliminated and This Generates Either a New Double Bond or a New Ring.