How does the DNA repair enzyme photolyase help prevent skin cancer?

Photolyase is an enzyme that specifically repairs damage in DNA caused by exposure to ultraviolet (UV) light. One of the common types of DNA damage caused by UV light is the formation of thymine dimers. This is where two adjacent thymine bases, which are one of the four nucleotide bases in DNA, bond together improperly when subjected to UV radiation. This type of damage disrupts the normal base pairing and can result in mutations during DNA replication if not corrected.

The photolyase enzyme works by binding to the site of the DNA where the thymine dimer has formed. It then absorbs energy from visible light (usually blue light) and uses this energy to break the abnormal chemical bond between the two thymine bases, restoring them to their original structure without the dimer. This process is often referred to as photoreactivation.

By repairing thymine dimers before the DNA is replicated, photolyase helps maintain the integrity of the genetic information and prevents mutations that could lead to skin cancer. During DNA replication, mutations can lead to incorrect coding for proteins, potentially causing cells to grow in an uncontrolled manner and giving rise to cancerous growths. Therefore, photolyase plays a critical role in preventing skin cancer by reversing the DNA damage caused by UV exposure.