Enzyme That Repairs Oxidized DNA Found in Mammalian Cells

Breimer reported in Biochemistry in 1983 that an enzyme called urea-DNA glycosylase, previously known only from the bacterium Escherichia coli, also exists in mammalian cells. This is a laboratory biochemistry study, not a skin or wound-healing study: it is about how cells repair DNA damage caused by oxidizing chemicals.

The researcher found the enzyme in extracts from calf thymus tissue and from human fibroblasts, a type of connective-tissue cell. The enzyme works on double-stranded polydeoxyribonucleotide, a chain of linked DNA building blocks, whose thymine units (one of DNA's four bases) had been chemically damaged using potassium permanganate and sodium hydroxide. The enzyme snips out a damaged piece and releases it as free urea, which was confirmed using a second enzyme, urease, that specifically breaks down urea.

Breimer purified the calf thymus version of the enzyme 400-fold and separated it from other known DNA-repair enzymes in mammals. It weighs about 25,000 daltons and needs no helper molecules to function. The study describes basic enzyme mechanics in cell extracts; it does not test the enzyme in whole animals, in people, or in any skin or cosmetic context.