氧化胁迫对Alkalibacterium sp. F26防御酶和辅因子的影响

Effects of Oxidative Challenge on Defensive Enzyme and Cofactors Level in Alkalibacterium sp. F26

摘要:

将一株能够高产过氧化氢酶的低度嗜盐嗜碱菌Alkalibacterium sp. F26作为模式微生物, 采用高效液相色谱技术测定胞内代谢物浓度, 研究氧化胁迫对其防御酶活性和辅因子的影响。研究结果表明：相比低浓度H2O2 (<1 mmol/L )胁迫, 此菌株在高浓度H2O2(>1 mmol/L )胁迫下的应答表现更为明显：经3 mmol/L H2O2胁迫后胞内CAT 酶活为106.54 U/mg protein, 是对照产量的1.76倍; ATP浓度则从对照浓度20.55 mmol/L下降到17.80 mmol/L; NAD+浓度自对照样品的69.89 mmol/L减少至31.77 mmol/L。由于ATP和NAD+浓度的减少, 相比未经过H2O2胁迫菌体, 细胞能荷值EC从0.77降低至0.68, NADH/NAD+则从0.08增加至0.41。然而, 这种应答机制在细胞受到低浓度H2O2的胁迫后并不明显：除发现100 mmol/L H2O2能够导致细胞防御机制的激活而使胞内ATP浓度相比对照有所增加的情况外, 经50 mmol/L和500 mmol/L H2O2胁迫后胞内ATP水平从对照的22.69 mmol/L只下降到22.38 mmol/L和13.70 mmol/L; 并且此种胁迫条件下NADH浓度变化也不显著。

Abstract:

In this paper, a slight halophilic alkaliphile strain, Alkalibacterium sp. F26, which produced high level of intracellular CAT observed in previous research, was selected as a model microbial to explain the responses of this bacterium to oxidative stress. The results indicated that Alkalibacterium sp. F26 had obvious responses to higher concentration (>1 mmol/L) of H2O2 than that to lower H2O2 (<1 mmol/L) challenge from the aspects of defensive enzyme synthesis and cofactors level variation. As for catalase production, the activity increased up to 106.54 U/mg protein which was 1.76 fold of the control when cells were challenged by 3 mmol/L H2O2, but its activity only was 1.13 fold when H2O2 was 100 mmol/L. As far as energy state was concerned, ATP production and NAD+ generation were significantly inhibited from 20.55 mmol/L to 17.80 mmol/L and 69.89 mmol/L to 31.77 mmol/L, respectively, leading to the drop of energy charge from 0.77 to 0.68 and the increase of the portion of NADH/NAD+ from 0.08 to 0.41 in the former case. However, these effects were less distinct under lower concentration of H2O2. Except of the condition of 100 mmol/L H2O2, under which the activation of defensive mechanism resulted in an increase of ATP, the level of ATP dropped from 22.69 mmol/L of the control to 22.38 mmol/L and 13.70 mmol/L when challenged by 50 mmol/L and 500 mmol/L H2O2. Besides, the concentration of NADH fluctuated and the NAD+ gradually reduced when H2O2 below 1 mmol/L.