关键词: 黄嘌呤脱氢酶, 耐辐射异常球菌, 氧化胁迫, xdhA

Abstract: Xanthine dehydrogenase is widely distributed in eukaryotes, bacteria and archaea. It is a redox enzyme that catalyzes the oxidation of various heterocyclic molecules such as purine, pteridine and aldehydes, and is related to nitrogen assimilation, hormone metabolism, aging regulation and reactive oxygen species generation. Deinococcus radiodurans R1 has strong resistance to oxidative stress and oxygen protection mechanism, and has a complete set of xanthine dehydrogenase coding gene (xdhABC)  in its genome. To explore the function of this enzyme, xdhA deleted mutant strain was constructed. Comparing the sensitivity of mutant strains ΔxdhA and wild type strain to purine metabolism and formaldehyde, determine xdhABC encoding protein of xanthine dehydrogenases. Compared with wild type strain, the viability of ΔxdhA was 2 orders of magnitude lower, and its survivability declined, and led to down-regulation of oxidative resistance genes after following exposure to 60 mmol·L^-1  H₂O₂. The analysis of in vitro enzymatic activity further demonstrated that ΔxdhA mutant strain resulted in a decrease in total antioxidant capacity under shock conditions. Therefore, it was speculated that D. radiodurans R1 xanthine dehydrogenase played an important role in the oxidative stress response.

Key words: xanthine dehydrogenase, D. radiodurans R1, oxidative stress, xdhA