Vergauwen Bjorn, Pauwels Frederik, Van Beeumen Jozef J
Laboratory for Protein Biochemistry and Protein Engineering, Ghent University, 9000 Ghent, Belgium.
J Bacteriol. 2003 Sep;185(18):5555-62. doi: 10.1128/JB.185.18.5555-5562.2003.
Glutathione is an abundant and ubiquitous low-molecular-weight thiol that may play a role in many cellular processes, including protection against the deleterious effects of reactive oxygen species. We address here the role of glutathione in protection against hydrogen peroxide (H2O2) in Haemophilus influenzae and show that glutathione and catalase provide overlapping defense systems. H. influenzae is naturally glutathione deficient and imports glutathione from the growth medium. Mutant H. influenzae lacking catalase and cultured in glutathione-deficient minimal medium is completely devoid of H2O2 scavenging activity and, accordingly, substantial amounts of H2O2 accumulate in the growth medium. H. influenzae generates H2O2 at rates similar to those reported for Escherichia coli, but the toxicity of this harmful metabolite is averted by glutathione-based H2O2 removal, which appears to be the primary system for protection against H2O2 endogenously generated during aerobic respiration. When H2O2 concentrations exceed low micromolar levels, the hktE gene-encoded catalase becomes the predominant scavenger. The requirement for glutathione in protection against oxidative stress is analogous to that in higher and lower eukaryotes but is unlike the situation in other bacteria in which glutathione is dispensable for aerobic growth during both normal and oxidative stress conditions.
谷胱甘肽是一种丰富且普遍存在的低分子量硫醇，可能在许多细胞过程中发挥作用，包括抵御活性氧的有害影响。我们在此探讨谷胱甘肽在流感嗜血杆菌中抵御过氧化氢（H2O2）的作用，并表明谷胱甘肽和过氧化氢酶提供了重叠的防御系统。流感嗜血杆菌天然缺乏谷胱甘肽，并从生长培养基中摄取谷胱甘肽。在缺乏谷胱甘肽的基本培养基中培养的缺乏过氧化氢酶的流感嗜血杆菌突变体完全没有H2O2清除活性，因此，大量的H2O2在生长培养基中积累。流感嗜血杆菌产生H2O2的速率与报道的大肠杆菌相似，但这种有害代谢物的毒性通过基于谷胱甘肽的H2O2清除得以避免，这似乎是抵御有氧呼吸过程中内源性产生的H2O2的主要系统。当H2O2浓度超过低微摩尔水平时，hktE基因编码的过氧化氢酶成为主要的清除剂。抵御氧化应激对谷胱甘肽的需求与高等和低等真核生物中的情况类似，但与其他细菌不同，在其他细菌中，无论是正常条件还是氧化应激条件下，谷胱甘肽对于有氧生长都是可有可无的。
