综述与专论: 纳米酶的抗菌机理与应用

细菌耐药性和抗生素滥用是一个世界性难题,需要开发新型抗菌剂,既能够高效杀菌,又能避免耐药性问题并具有较好的生物和环境相容性．纳米酶具有调控ROS自由基的能力,可以高效杀死多种革兰氏阳性和阴性致病菌以及顽固性生物膜;同时纳米酶具有较好的稳定性、生物相容性、可回收再利用等优点,在促进伤口愈合、龋齿防治和环境防污方面具有重要的应用前景．     

基于纳米酶的无抗生素抗菌策略

抗生素是抵抗细菌感染的有力武器,然而抗生素的过量使用和滥用加速了细菌耐药性的发展,严重威胁人类健康。开发高效和广谱的无抗生素抗菌策略迫在眉睫。以过氧化氢(H₂O₂)为代表的活性氧(reactive oxygen species, ROS)能氧化多种生物分子,使其结构和活性改变而发挥广谱抗菌作用,是无抗生素抗菌策略之一。然而,临床常用的H₂O₂浓度较高(0.5%～3%),会刺激皮肤和延缓伤口愈合。利用过氧化物酶催化H₂O₂生成氧化性更强的羟自由基(·OH),可大幅提高ROS抗菌策略的性能。然而,天然酶生产成本高、稳定性低等缺点限制了该策略的推广。纳米酶是具有类似天然酶催化活性的纳米材料的统称。与天然酶相比,纳米酶具有制备简单、成本低和易储存等优势,是开发基于ROS的无抗生素抗菌策略的良好选择。贵金属、金属氧化物、金属硫化物、金属有机框架、碳基纳米材料等多种纳米材料具有过氧化物酶、氧化酶等的模拟催化活性,基于这些材料的纳米酶抗菌研究层出不穷,本文将对这些研究进...     

水生生物体内抗氧化酶及其影响因素研究进展

生物体在新陈代谢过程中,细胞内会产生少量的自由基,参与了机体内多种生理过程,具有重要的生理功能。但是在一些应激因子的作用下,体内产生的活性氧大量积累,将会对细胞产生损伤,抗氧化酶类在清除体内活性氧的过程中具有重要作用。在综述了抗氧化酶的分类、结构特点及相互间作用的基础上,阐述了水生生物体内抗氧化酶及其影响因素的研究进展。     

锰氧化细菌的生理生态功能与作用机制研究进展

锰的生物地球化学循环过程与全球尺度的营养元素循环紧密联系,是影响全球生态平衡及气候变化的重要因素之一。在自然界中,锰元素主要以氧化锰和含氧酸盐的矿物形式存在,近年来的研究观点普遍认为细菌介导的氧化作用是自然环境中锰氧化物形成的主要原因。锰氧化细菌广泛分布于海洋、锰矿土壤等生态系统,近期在植物微生态系统中也被发现,其生理生态功能未知。细菌的锰氧化过程是一个复杂的过程,多铜氧化酶和过氧化物(氢)酶是参与该过程的主要酶类,但关于其催化机制的认识尚不成熟。本综述系统探讨锰氧化细菌的种类和分布、细菌锰氧化作用的生理生态功能、参与细菌锰氧化作用的功能酶及其分子机制,总结这一研究领域所取得的成果和仍未解决的科学问题,并对今后的发展方向进行展望。     

铁死亡发生机制的研究进展

铁死亡(ferroptosis)是近几年发现的一种新的细胞死亡方式,是在小分子物质诱导下发生的氧化性细胞死亡,具有铁离子依赖性.其发生是细胞内脂质活性氧(reactive oxygen species,ROS)生成与降解的平衡失调所致.铁死亡诱导剂通过不同的通路直接或间接作用于谷胱甘肽过氧化物酶(glutathione peroxidase,GPXs),导致细胞抗氧化能力降低、ROS堆积、最终引起细胞氧化性死亡.铁死亡与帕金森综合征、胰腺癌等多种疾病相关,并发现可以通过激活或抑制铁死亡来干预疾病的发展,因此铁死亡成为近年来的研究热点.本文就铁死亡的发现、特点、发生机制及其与疾病的关系展开论述,将近年研究成果进行总结,期望为以铁死亡为基础的疾病治疗提供参考.     

AmpC酶及其分子生物学检测

随着抗生素的大量使用,细菌耐药问题日益突出,其中β-内酰胺类药是临床应用最多的抗生素。而药物被β-内酰胺酶水解灭活是细菌耐药的主要原因。近年来革兰阴性杆菌中,AmpC酶(属Bush-J-M1群)已逐渐成为临床面临的严重治疗问题。本文简要介绍AmpC酶的一般特性,产酶基因的结构、功能和表达调控。另外,与几种传统的检测该酶的方法相比,分子生物学方法准确性高,且特异性好,文中重点介绍了PCR,核酸分子杂交,核酸序列分析等方法。     

植物过氧化物酶体在活性氧信号网络中的作用

过氧化物酶体是高度动态、代谢活跃的细胞器,主要参与脂肪酸等脂质的代谢及产生和清除不同的活性氧(reactive oxygen species, ROS)。ROS是细胞有氧代谢的副产物。当胁迫长期作用于植物,过量的ROS会引起氧胁迫,损害细胞结构和功能的完整性,导致细胞代谢减缓,活性降低,甚至死亡;但低浓度的ROS则作为分子信号,感应细胞ROS/氧化还原变化,从而触发由环境因素导致的过氧化物酶体动力学以及依赖ROS信号网络改变而产生快速、特异性的应答。ROS也可以通过直接或间接调节细胞生长来控制植物的发育,是植物发育的重要调节剂。此外,过氧化物酶体的动态平衡由ROS、过氧化物酶体蛋白酶及自噬过程调节,对于维持细胞的氧化还原平衡至关重要。本文就过氧化物酶体中ROS的产生和抗氧化剂的调控机制进行综述,以期为过氧化物酶体如何感知环境变化,以及在细胞应答中,ROS作为重要信号分子的研究提供参考。     

植物过氧化物酶体在活性氧信号网络中的作用北大核心CSCD

过氧化物酶体是高度动态、代谢活跃的细胞器,主要参与脂肪酸等脂质的代谢及产生和清除不同的活性氧(reactive oxygen species,ROS)。ROS是细胞有氧代谢的副产物。当胁迫长期作用于植物,过量的ROS会引起氧胁迫,损害细胞结构和功能的完整性,导致细胞代谢减缓,活性降低,甚至死亡;但低浓度的ROS则作为分子信号,感应细胞ROS/氧化还原变化,从而触发由环境因素导致的过氧化物酶体动力学以及依赖ROS信号网络改变而产生快速、特异性的应答。ROS也可以通过直接或间接调节细胞生长来控制植物的发育,是植物发育的重要调节剂。此外,过氧化物酶体的动态平衡由ROS、过氧化物酶体蛋白酶及自噬过程调节,对于维持细胞的氧化还原平衡至关重要。本文就过氧化物酶体中ROS的产生和抗氧化剂的调控机制进行综述,以期为过氧化物酶体如何感知环境变化,以及在细胞应答中,ROS作为重要信号分子的研究提供参考。     

活性氧调控植物生长发育的研究进展

活性氧(ROS)是植物有氧代谢过程中的副产物, 它在植物的许多生命过程中均具有有害和有利的双重功能。ROS对细胞的氧化损伤作用和信号转导诱导植物防卫反应已有详尽的研究。近年来, 越来越多的关于ROS调控植物生长发育的证据开始引起了人们的广泛关注。细胞的生长是植物发育的重要部分, ROS通过直接或间接调节细胞的生长来控制植物的发育, 成为植物发育的重要调节剂。该文综述了羟自由基(.OH)及其前体超氧阴离子自由基(O2^–. )和过氧化氢(H₂O₂)调控植物生长发育的研究进展, 包括ROS调控植物不同器官生长的证据和机理、ROS产生的途径及其检测方法, 同时对今后的研究进行了展望。     

动物血红素过氧化物酶参与细菌氧化Mn(Ⅱ)的研究进展

锰氧化物是自然环境中一种重要的高活性矿物,在多种元素的生物地球化学循环中起着重要作用。细菌对锰氧化物的形成具有推动作用。截至目前,研究者已从环境中分离出多株锰氧化细菌,并在氧化机理的研究上取得了一定的进展。目前细菌中已知的锰氧化酶包括多铜氧化酶和动物血红素过氧化物酶。与多铜氧化酶相比,动物血红素过氧化物酶在蛋白结构与氧化方式上都具有自己的特点。本文结合国内外最新研究结果,在氧化菌株、氧化酶和基因、氧化方式及影响因素等方面对动物血红素过氧化物酶参与细菌氧化Mn(Ⅱ)的研究进行了总结,对未来研究方向进行了展望。     

Inhibitory effects of flavonoids on alternative respiration of plant mitochondria

Inhibitory effects of flavonoids on plant alternative respiration were investigated using isolated mitochondria of Vigna radiata seedlings. The antioxidant flavonoids quercetin and myricetin effectively inhibited alternative respiration. We suggest that radical scavenging activity is involved in the inhibitory mechanism.     

Mechanisms for the generation of reactive oxygen species in plant defence response

Recent data indicate that plants, in a manner similar to the situation found in mammalian phagocytotic cells, produce reactive oxygen species (ROS) in response to pathogen infection. This reaction could be very quick when using pre-existing, usually exocellular, components and/or, when biochemical machinery of the cell is activated, relatively late and long-lasting. The oxidative burst is defined as a rapid, transient production of high levels of ROS in response to external stimuli. Two major models depicting the origin of ROS in the oxidative burst are described, namely: the NADPH oxidase system and the pH-dependent generation of hydrogen peroxide by exocellular peroxidases. Additionally, the participation of exocellular ROS-generating enzymes, like germin-like oxalate oxidases and amine oxidases, in plant defence response is demonstrated. The involvement of protoplasmic ROS-generating systems is also indicated.     

Hydrogen peroxide: a Jekyll and Hyde signalling molecule

Reactive oxygen species (ROS) are a group of molecules produced in the cell through metabolism of oxygen. Endogenous ROS such as hydrogen peroxide (H₂O₂) have long been recognised as destructive molecules. The well-established roles they have in the phagosome and genomic instability has led to the characterisation of these molecules as non-specific agents of destruction. Interestingly, there is a growing body of literature suggesting a less sinister role for this Jekyll and Hyde molecule. It is now evident that at lower physiological levels, H₂O₂ can act as a classical intracellular signalling molecule regulating kinase-driven pathways. The newly discovered biological functions attributed to ROS include proliferation, migration, anoikis, survival and autophagy. Furthermore, recent advances in detection and quantification of ROS-family members have revealed that the diverse functions of ROS can be determined by the subcellular source, location and duration of these molecules within the cell. In light of this confounding paradox, we will examine the factors and circumstances that determine whether H₂O₂ acts in a pro-survival or deleterious manner.     

The relationship between respiration rate and peroxidase activities in maize root mitochondria

In the present study we provide the evidence of different respiration rates and peroxidase activities in maize (Zea mays L.) mitochondria isolated from germinated seeds and roots of 2-week-old seedlings. The negative relationships between mitochondrial respiration rate measured with NADH as substrate and activities of peroxidases that oxidized NADH in both oxidative and peroxidative cycles were found. The possible role of peroxidase in the regulation of reactive oxygen species metabolism in expense of NADH oxidation was hypothesized.     

Evidence of mitochondrial involvement in the transduction of signals required for the induction of genes associated with pathogen attack and senescence

Using the mRNA differential display technique, seven cDNAs have been isolated that are rapidly induced when cultured tobacco (Nicotiana tabacum) cells are treated with the mitochondrial electron transport inhibitor antimycin A (AA). Interestingly, six of the cDNAs show distinct similarity to genes known to be induced by processes that involve programmed cell death (PCD), such as senescence and pathogen attack. All of the cDNAs as well as Aox1, a gene encoding the alternative oxidase, were found to also be strongly induced by H2O2 and salicylic acid (SA). AA, H2O2 and SA treatment of tobacco cells caused a rapid rise in intracellular ROS accumulation that, when prevented by antioxidant treatment, resulted in inhibition of gene induction. Besides AA, both H2O2 and SA were found to disrupt normal mitochondrial function resulting in decreased rates of electron transport and a lowering of cellular ATP levels. Furthermore, the pre-treatment of tobacco cells with bongkrekic acid, a known inhibitor of the mitochondrial permeability transition pore in animal cells, was found to completely block gene induction when AA, H2O2 or SA were subsequently added. These findings suggest that the mitochondrion may serve an important role in conveying intracellular stress signals to the nucleus, leading to alterations in gene expression.     

信号配体诱导的活性氧生成

活性氧(reactiveoxygenspecies,ROS)是生物体内一类活性含氧化合物的总称,主要包括超氧阴离子、羟自由基和过氧化氢等。细胞内有多种部位能生成ROS,主要包括线粒体、内质网、NADPH氧化酶复合体、脂氧合酶系、环氧合酶系等。静息条件下,细胞内ROS的水平被控制在很低的范围。而在细胞受到各种生理或病理因素作用时,当多种细胞外信号分子作用于其膜受体,ROS生成可以受到受体活化的诱导而“有目的”地快速增加,从而作为细胞内信号分子参与细胞增殖,分化和凋亡等各种细胞行为。     

Unravelling mitochondrial retrograde regulation in the abiotic stress induction of rice ALTERNATIVE OXIDASE 1 genes

Mitochondrial retrograde regulation (MRR) is the transduction of mitochondrial signals to mediate nuclear gene expression. It is not clear whether MRR is a common regulation mechanism in plant abiotic stress response. In this study, we analysed the early abiotic stress response of the rice OsAOX1 genes, and the induction of OsAOX1a and OsAOX1b (OsAOX1a/b) was selected as a working model for the stress‐induced MRR studies. We found that the induction mediated by the superoxide ion (O_2·^‐)‐generating chemical methyl viologen was stronger than that of hydrogen peroxide (H₂O₂). The addition of reactive oxygen species (ROS) scavengers demonstrated that the stress induction was reduced by eliminating O_2·^‐. Furthermore, the stress induction did not rely on chloroplast‐ or cytosol‐derived O_2·^‐. Next, we generated transgenic plants overexpressing the superoxide dismutase (SOD) gene at different subcellular locations. The results suggest that only the mitochondrial SOD, OsMSD, attenuated the stress induction of OsAOX1a/b specifically. Therefore, our findings demonstrate that abiotic stress initiates the MRR on OsAOX1a/b and that mitochondrial O_2·^– is involved in the process.     

NADPH oxidase produces reactive oxygen species and maintains survival of rat astrocytes

Reactive oxygen species (ROS) produced by activated astrocytes have been considered to be involved in the pathogenesis of neurodegenerative diseases, while NADPH oxidase is an essential enzyme involved in ROS-mediated signal transduction. The goal of the present study was to determine whether NADPH oxidase plays a role in ROS generation and cell survival in rat astrocytes. We found that the release of ROS in rat astrocytes was significantly increased by stimulation with calcium ionophore or opsonized zymosan, which are known to trigger a respiration burst in phagocytes by the NADPH oxidase pathway. Further study indicated that diphenylene iodonium (DPI), an inhibitor of NADPH oxidase, significantly suppressed the increase of ROS release caused by the calcium ionophore or opsonized zymosan. Cell survival assay and fluorescence double dyeing with acridine orange and ethidium bromide showed that DPI dose- and time-dependently decreased the viability of normal astrocytes, whereas exogenous supplementation of H2O2 can reverse the survival of DPI-treated astrocytes. For the first time, our results suggest that NADPH oxidase is an important enzyme for the generation of ROS in astrocytes, and the ROS generated by NADPH oxidase play an essential role in astrocyte survival.