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排序方式: 共有222条查询结果,搜索用时 11 毫秒
141.
Vic Shao-Chih Chiang 《Critical reviews in food science and nutrition》2017,57(6):1153-1173
Red meat is consumed globally and plays an important role in the Western diet. Its consumption is however linked with various types of diseases. This review focuses on the relationship of red meat with cancer, its dependency on the thermal processing methodology and the subsequent physiological effects. The epidemiological evidence is discussed, followed by introduction of the species that were hypothesized to contribute to these carcinogenic effects including polycyclic aromatic hydrocarbons (PAHs), heterocyclic amines (HCAs), N-nitroso compounds (NOCs), heme iron, and macromolecular oxidation products. Their carcinogenic mechanisms were then addressed with further emphasis on the involvement of inflammation and oxidative stress. The thermal processing dependency of the carcinogen generation and the partially elucidated carcinogenic mechanism both represent doorways of opportunities available for the scientific manipulation of their impact after human consumption, to minimize the cancer risks associated with red meat. 相似文献
142.
Loola Al‐Kassim Z Wang Arthur G Szabo Keith E Taylor Bulent Mutus 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(9):1026-1030
We have prepared a novel oxygen carrier composed of Starburst dendrimer 3 hematoporphyrin iron(III) di‐1‐(3‐aminopropyl)imidazole di‐succinic acid (SDHAPI). This compound has a molecular weight of ~12.7 kD. O2 and CO binding to SDHAPI was demonstrated by UV‐vis spectroscopy. Oxygenated SDHAPI had an estimated auto‐oxidation half‐life of 24 min. The oxygen stoichiometry (~6 mol of O2 mol?1 SDHAPI) and the kobs(on+off) of 0.084 s?1 and kobs(off) of 0.009 s?1 were estimated with an oxygen electrode. Copyright © 2005 Society of Chemical Industry 相似文献
143.
Kobayashi K Kubo M Yoshioka S Kitagawa T Kato Y Asano Y Aono S 《Chembiochem : a European journal of chemical biology》2006,7(12):2004-2009
Phenylacetaldoxime dehydratase from Bacillus sp. OxB-1 (OxdB) contains a heme that acts as the active site for the dehydration reaction of aldoxime. Ferrous heme is the active form, in which the heme is five coordinate with His282 as a proximal ligand. In this work, we evaluated the functional role of the proximal ligand for the catalytic properties of the enzyme by "the cavity mutant technique". The H282G mutant of OxdB lost enzymatic activity, although the heme, which was five coordinate with a water molecule (or OH-) as an axial ligand, existed in the protein matrix. The enzymatic activity was rescued by imidazole or pyridine derivatives that acted as the exogenous proximal ligand. By changing the electron-donation ability of the exogenous ligand with different substituents, the enzymatic activity could be regulated systematically. The stronger the electron-donation ability of the exogenous ligand, the higher was the restored enzymatic activity. Interestingly, H282G OxdB with 2-methyl imidazole showed a higher activity than the wild-type enzyme. Kinetic analyses revealed that the proximal His regulated not only the affinity of substrate binding to the heme but also the elimination of the OH group from the substrate. 相似文献
144.
Hepatoprotective effects of different combinations of sweet orange,Unshiu mikan,and mini tomato juice powders against tert‐butyl hydroperoxide‐induced oxidative stress in HepG2 cells 下载免费PDF全文
145.
Worrall JA Diederix RE Prudêncio M Lowe CE Ciofi-Baffoni S Ubbink M Canters GW 《Chembiochem : a European journal of chemical biology》2005,6(4):747-758
The effect on the heme environment upon unfolding Paracoccus versutus ferricytochrome c-550 and two site-directed variants, K99E and H118Q, has been assessed through a combination of peroxidase activity increase and one-dimensional NMR spectroscopy. At pH 4.5, the data are consistent with a low- to high-spin heme transition, with the K99E mutation resulting in a protein with increased peroxidase activity in the absence of or at low concentrations of denaturant. Furthermore, the mobility of the polypeptide chain at pH 4.5 for the wild-type protein has been monitored in the absence and presence of denaturant through heteronuclear NMR experiments. The results are discussed in terms of local stability differences between bacterial and mitochondrial cytochromes c that are inferred from peroxidase activity assays. At pH 7.0, a mixture of misligated heme states arising from protein-based ligands assigned to lysine and histidine is detected. At low denaturant concentrations, these partially unfolded misligated heme forms inhibit the peroxidase activity. Data from the K99E mutation at pH 7.0 indicate that K99 is not involved in heme misligation, whereas histidine coordination is proven by the data from the H118Q variant. 相似文献
146.
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148.
The Thr–His Connection on the Distal Heme of Catalase‐Related Hemoproteins: A Hallmark of Reaction with Fatty Acid Hydroperoxides 下载免费PDF全文
Dr. Zahra Mashhadi Prof. Marcia E. Newcomer Prof. Alan R. Brash 《Chembiochem : a European journal of chemical biology》2016,17(21):2000-2006
This review focuses on a group of heme peroxidases that retain the catalase fold in structure, yet show little or no reaction with hydrogen peroxide. Instead of having a role in oxidative defense, these enzymes are involved in secondary metabolite biosynthesis. The prototypical enzyme is catalase‐related allene oxide synthase, an enzyme that converts a specific fatty acid hydroperoxide to the corresponding allene oxide (epoxide). Other catalase‐related enzymes form allylic epoxides, aldehydes, or a bicyclobutane fatty acid. In all catalases (including these relatives), a His residue on the distal face of the heme is absolutely required for activity. Its immediate neighbor in sequence as well as in 3 D space is conserved as Val in true catalases and Thr in the fatty acid hydroperoxide‐metabolizing enzymes. Thr–His on the distal face of the heme is critical in switching the substrate specificity from H2O2 to fatty acid hydroperoxide. 相似文献
149.
Enhancement of Peroxidase Activity in Artificial Mimochrome VI Catalysts through Rational Design 下载免费PDF全文
Dr. Giorgio Caserta Dr. Marco Chino Dr. Vincenzo Firpo Dr. Gerardo Zambrano Dr. Linda Leone Dr. Daniele D'Alonzo Prof. Flavia Nastri Dr. Ornella Maglio Prof. Vincenzo Pavone Prof. Angela Lombardi 《Chembiochem : a European journal of chemical biology》2018,19(17):1823-1826
Rational design provides an attractive strategy to tune and control the reactivity of bioinspired catalysts. Although there has been considerable progress in the design of heme oxidase mimetics with active‐site environments of ever‐growing complexity and catalytic efficiency, their stability during turnover is still an open challenge. Herein, we show that the simple incorporation of two 2‐aminoisobutyric acids into an artificial peptide‐based peroxidase results in a new catalyst (FeIII‐MC6*a) with higher resistance against oxidative damage and higher catalytic efficiency. The turnover number of this catalyst is twice as high as that of its predecessor. These results point out the protective role exerted by the peptide matrix and pave the way to the synthesis of robust bioinspired catalysts. 相似文献
150.