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Biology of microbes
Published in Philip A. Geis, Cosmetic Microbiology, 2006
The latter two are sometimes contaminants of personal care products, so we will touch briefly on nitrogen fixation. Realize, however, that nitrogen fixation is primarily a function of organisms that are not of concern to the cosmetic or drug microbiologist. Nitrogen fixation is the reduction of atmospheric gaseous nitrogen into ammonia by nitrogenase. It requires at least 6 electrons for reducing power and 12 ATP molecules.
Affinity Modification — Organic Chemistry
Published in Dmitri G. Knorre, Valentin V. Vlassov, Affinity Modification of Biopolymers, 1989
Dmitri G. Knorre, Valentin V. Vlassov
An irreversible inhibition of nitrogenase (EC 1.18.2.1) observed in the presence of nitric oxide and nitrite can also be ascribed to the affinity modification process. This enzyme catalyzes the reduction of N2 to NH3 in the ATP-dependent reaction. It was proposed that the inactivating species is the NO molecule which imitates the enzyme substrate, binds to the protein, and disrupts in some way the essential for catalytic activity Fe4S4 cluster present in this enzyme.202 Sometimes a small ligand can be imitated by part of the structure of a larger molecule. Thus, inorganic phosphate was imitated by the affinity reagents methylphosphate and even 4-azido-2-nitrophenyl phosphate. The first reagent efficiently alkylated active-site carboxyl residues in inorganic pyrophosphatase (EC 3.6.1.1).203 The other reagent was used for photoaffinity modification of mitochondrial adenosine triphosphatase (EC 3.6.1.3) at the single inorganic phosphate binding site present in this enzyme.204 In more complex molecules this situation is routine and very often only part of the reagent structure is involved in recognition. Thus, in the affinity reagent p-iodoacetamidosalicylic acid XIX synthesized by Backer in the very beginning of the affinity modification studies, only a small part of the structure imitates lactate, the substrate of lactate dehydrogenase (see Section II.A).
The Genetics of the Frankia-Actinorhizal Symbiosis
Published in Peter M. Gresshoff, Molecular Biology of Symbiotic Nitrogen Fixation, 2018
Pascal Simonet, Philippe Normand, Ann M. Hirsch, Antoon D. L. Akkermans
Normand and co-workers57 have used the nifHD region of Frankia ArI3 as an homologous probe to detect nif RFLPs. For most Alnus-compatible strains tested, hybridization occurred with an 8 kb BamHI fragment and a 10-kb BglII fragment. With SstI, which has more sites, hybridization was strictly restricted to the nif genes and occurred in all Alnus-compatible strains with two fragments of 1.3 and 0.4 kb. These data and those obtained with other Frankia strains confirm the observations of Hennecke et al.58 on nitrogenase genes of other nitrogen-fixing microorganisms. Among nitrogenase genes, nifH appeared to be the most conserved. The degree of similarity is very high for strains for which close relationships have been determined with other criteria, and less for more divergent strains. Similar ob servation were found for nifD gene with a higher amplitude of the divergences observed for more divergent strains. This means that nitrogenase genes are some of the most highly conserved portions of the genome, as mentioned by An et al.,30 however, sufficiently divergent to provide information on relationships between strains. Hennecke et al.58 have demonstrated that the nitrogenase genes and 16S rRNA have evolved in parallel, which provides powerful tools to study nitrogen-fixing bacteria. Such results argue against the idea of lateral transfer of genes between nitrogen-fixing bacteria, and for the notion that nif genes have evolved in parallel and independently in the bacteria that carry them. These observations further suggest that measurement of nif sequence similarity could be used as a taxonomic criterion in addition to 16S rRNA.
An overview on cyanobacterial blooms and toxins production: their occurrence and influencing factors
Published in Toxin Reviews, 2022
Isaac Yaw Massey, Muwaffak Al osman, Fei Yang
It is well established that nitrogen fixation is an important feature of some cyanobacteria species and in terms of nutrition nitrogen-fixing, cyanobacteria are considered the most self-sufficient among other organisms. They are photoautotrophs that require only light energy, CO2, dinitrogen (N2), water and some minerals (Paerl and Huisman 2009, Paerl and Otten 2013, Paerl et al.2016, 2001). Heterocysts are specialized nitrogen-fixing cells. Heterocysts have thick cell wall, do not pose photosynthetic membrane and are larger, clearer and highly refractive under light microscope appearance. They may occur within the filament of photosynthetic cells or terminally on a filament (Paerl and Huisman 2009, Paerl and Otten 2013, Paerl et al.2016, 2001). Due to the differences in size, shape and location of heterocysts, they form a significant component in species identification. Within the heterocysts, the enzyme nitrogenase reduces molecular nitrogen to ammonia, which is incorporated into the amido group of glutamine. The thickened cell wall enables molecular oxygen to enter the cell, to be reduced (Bryant 1994, Paerl et al.2016, 2001), thus helping to maintain a highly reducing environment within the cell, necessary for nitrogen reduction.
Detrimental effect of UV-B radiation on growth, photosynthetic pigments, metabolites and ultrastructure of some cyanobacteria and freshwater chlorophyta
Published in International Journal of Radiation Biology, 2021
Mostafa M. El-Sheekh, Eman A. Alwaleed, Aml Ibrahim, Hani Saber
Increasing the protein content was in agreement with previous results on Scenedesmus quadricauda (Kovacik et al. 2010) and Ulva lactuca and Sargassum hornchuchii (Noaman et al. 2016) to have the ability for adaptation to environmental stresses including UV radiation by increasing protein content (Jiménez et al. 2004; Tominaga et al. 2010). Decreasing in protein contents under UV-B stress agree with the results observed by Prasad et al. (1998) on Chlorella vulgaris, Chaturvedi and Shyam (2000) on Chlamydomonas reinhardtii, Bischof et al. (2000) on laminaria solidungula, Noaman (2007) on Synechococcus leopoliensis and Noaman et al. (2016) on Pterocladia capillacea. Xue et al. (2005) proved the degradation and destruction of protein in algae under UV radiation; this could be attributed to capacity of protein for absorption of UV radiation (Ziska and Teramura 1992). The reduction of protein synthesis may be due to inhibition of nitrogenase enzyme by UV (Kumar et al. 2003).
Nanomicelles for GLUT1-targeting hepatocellular carcinoma therapy based on NADPH depletion
Published in Drug Delivery, 2023
Congyi Zhang, Zehui Liu, Feng Wang, Bin Zhang, Xirui Zhang, Peiwen Guo, Tianwei Li, Sheng Tai, Changmei Zhang
Man-NIT not only has the excellent performance of nanocarrier, but also exhibits the capability of antitumor. With the increase of nanomicelle concentration, Man-NIT can effectively inhibit tumor growth. The nitroimidazole of Man-NIT will deplete NADPH under the action of nitrogenase. Our results showed that the content of NADPH in Man-NIT group was obviously decreased, which was consistent with the literature (Guo et al., 2020). It also reports that the increased production of NADPH and GSH can counteract oxidative stress and promote tumor cell survival and growth in mice (Tong et al., 2021). GSH can scavenge free radicals and peroxides, hence decline of GSH can lead to excessive ROS generation and cell apoptosis (Armstrong & Jones, 2002). GSSG is reduced to GSH by hydrogen supplied from NADPH under the action of glutathione reductase (GR). Therefore, NADPH plays an important role in maintaining the content of GSH in cells as a coenzyme of GR (Mejía et al., 2018; Moreno-Sanchez et al., 2018). So Man-NIT attenuates oxidative stress antioxidants, such as GSH, and inhibits tumor proliferation. When HCCLM3 cells were incubated with nanomicelles, NADPH depletion in cells would inevitably affect GSH synthesis, resulting in the decline of GSH content. Compared with control group, the GSH content of Man-NIT and PEG-NIT group decreased, which due to both nanomicelles containing nitroimidazole structure. Because of the blocked synthesis of GSH, the ability of counteracting oxidative stress and scavenging ROS in tumor cells will also be weakened. We used the fluorescent probe DCFH-DA to detect ROS and found ROS increased after HCCLM3 cells incubated with Man-NIT. If the high concentration of ROS in tumor cells cannot be timely reduced by GSH, it will lead to the imbalance of redox in cells and even tumor cell death. Man-NIT can promote the productions of ROS via NADPH depletion and decreasing GSH, subsequently aggravating lipid peroxidation and triggering cell death in HCC.