Schnell S, Steinman H M
Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
J Bacteriol. 1995 Oct;177(20):5924-9. doi: 10.1128/jb.177.20.5924-5929.1995.
Although cytosolic superoxide dismutases (SODs) are widely distributed among bacteria, only a small number of species contain a periplasmic SOD. One of these is Caulobacter crescentus, which has a copper-zinc SOD (CuZnSOD) in the periplasm and an iron SOD (FeSOD) in the cytosol. The function of periplasmic CuZnSOD was studied by characterizing a mutant of C. crescentus with an insertionally inactivated CuZnSOD gene. Wild-type and mutant strains showed identical tolerance to intracellular superoxide. However, in response to extracellular superoxide, the presence of periplasmic CuZnSOD increased survival by as much as 20-fold. This is the first demonstration that periplasmic SOD defends against external superoxide of environmental origin. This result has implications for those bacterial pathogens that contain a CuZnSOD. C. crescentus was shown to contain a single catalase/peroxidase which, like Escherichia coli KatG catalase/peroxidase, is present in both the periplasmic and cytoplasmic fractions. The growth stage dependence of C. crescentus catalase/peroxidase and SOD activity was studied. Although FeSOD activity was identical in exponential- and stationary-phase cultures, CuZnSOD was induced nearly 4-fold in stationary phase and the catalase/peroxidase was induced nearly 100-fold. Induction of antioxidant enzymes in the periplasm of C. crescentus appears to be an important attribute of the stationary-phase response and may be a useful tool for studying its regulation.
虽然胞质超氧化物歧化酶（SOD）在细菌中广泛分布，但只有少数物种含有周质SOD。其中之一是新月柄杆菌，它在周质中有一个铜锌SOD（CuZnSOD），在胞质中有一个铁SOD（FeSOD）。通过对一个插入失活CuZnSOD基因的新月柄杆菌突变体进行表征，研究了周质CuZnSOD的功能。野生型和突变体菌株对细胞内超氧化物表现出相同的耐受性。然而，在应对细胞外超氧化物时，周质CuZnSOD的存在使存活率提高了20倍之多。这是首次证明周质SOD能抵御环境来源的外部超氧化物。这一结果对那些含有CuZnSOD的细菌病原体具有重要意义。已证明新月柄杆菌含有单一过氧化氢酶/过氧化物酶，与大肠杆菌KatG过氧化氢酶/过氧化物酶一样，它存在于周质和细胞质部分。研究了新月柄杆菌过氧化氢酶/过氧化物酶和SOD活性对生长阶段的依赖性。虽然FeSOD活性在指数生长期和稳定期培养物中相同，但CuZnSOD在稳定期诱导增加了近4倍，过氧化氢酶/过氧化物酶诱导增加了近100倍。新月柄杆菌周质中抗氧化酶的诱导似乎是稳定期反应的一个重要特征，可能是研究其调控的一个有用工具。
