Metabolite damage can occur through enzyme promiscuity or spontaneous chemical reactions. Many metabolites are chemically reactive and unstable and can react with other cell components or undergo unwanted modifications. Enzymatically or chemically damaged metabolites are always useless and often toxic. To prevent toxicity that can occur from the accumulation of damaged metabolites, organisms have damage-control systems that:
# Reconvert damaged metabolites to their original, undamaged form (damage repair)
# Convert a potentially harmful metabolite to a benign one (damage pre-emption)
# Prevent damage from happening by limiting the build-up of reactive, but non-damaged metabolites that can lead to harmful products (directed overflow)
Damage-control systems can involve one or more specific enzymes.