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21.
22.
Valentina Battaglia Cristina Fiore Mauro Salvi Mario Palermo Antonio Toninello 《生物化学与生物物理学报:生物膜》2008,1778(1):313-323
Glycyrrhetinic acid (GE), a hydrolysis product of glycyrrhizic acid, one of the main constituents of licorice root, is able, depending on its concentration, to prevent or to induce the mitochondrial permeability transition (MPT) (a phenomenon related to oxidative stress) in rat heart mitochondria (RHM). In RHM, below a threshold concentration of 7.5 μM, GE prevents oxidative stress and MPT induced by supraphysiological Ca2+ concentrations. Above this concentration, GE induces oxidative stress by interacting with a Fe-S centre of Complex I, thus producing ROS, and amplifies the opening of the transition pore, once again induced by Ca2+. GE also inhibits Ca2+ transport in RHM, thereby preventing the oxidative stress induced by the cation. However, the reduced amount of Ca2+ transported in the matrix is sufficient to predispose adenine nucleotide translocase for pore opening. Comparisons between observed results and the effects of GE in rat liver mitochondria (RLM), in which the drug induces only MPT without exhibiting any protective effect, confirm that it interacts in a different way with RHM, suggesting tissue specificity for its action. The concentration dependence of the opposite effects of GE, in RHM but not RLM, is most probably due to the existence of a different, more complex, pathway by means of which GE reaches its target. It follows that high GE concentrations are necessary to stimulate the oxidative stress capable of inducing MPT, because of the above effect, which prevents the interaction of low concentrations of GE with the Fe-S centre. The reported results also explain the mechanism of apoptosis induction by GE in cardiomyocytes. 相似文献
23.
The mechanism of the aniline hydroxylase activity of methaemoglobin in a monooxygenase system consisting of NADH as electron donor, riboflavin, FAD, FMN or methylene blue as electron carrier and methaemoglobin as the terminal oxidase has been studied. Hydrogen peroxide is produced from oxygen in a methaemoglobin-independent process. 4-Aminophenol is subsequently produced peroxidatively by an NADH-dependent process; NADH prevents a further oxidation of 4-aminophenol in the presence of haemoglobin. In the absence of electron carrier, NADH slowly reduces haemoglobin and then oxyhaemoglobin reacts with aniline to give 4-aminophenol. In the absence of electron donor and electron carrier, oxyhaemoglobin and aniline give rise to the reversible production of 4-aminophenol. 相似文献
24.
The metabolism of adenine and guanine, relating to the biosynthesis of caffeine, in excised shoot tips of tea was studied with micromolar amounts of adenine-[8-14C] or guanine-[8-14C]. Among the presumed precursors of caffeine biosynthesis, adenine was the most effective, whereas guanine was the least effective. After administration of a ‘pulse’ of adenine-[8-14C], almost all of the adenine-[14C] supplied disappeared by 30 hr, and 14C-labelled caffeine and RNA purine nucleotide (AMP and GMP) synthesis increased throughout the experimental period, whereas the radioactivities of free purine nucleotides, 7-methylxanthine and theobromine increased during the first 10 hr incubation period, followed by a steady decrease. By contrast, more than 45% of the guanine-[8-14C] supplied remained unchanged even after a 120 hr period. The main products of guanine-[8-14C] metabolism in tea shoot tips were guanine nucleotides, theobromine, caffeine and the GMP of RNA. The results support the hypothesis that the purine nucleotides are synthesized from adenine and guanine via the pathway of purine salvage. Adenylate is readily converted into other purine nucleotides, whereas the conversion rate of guanylate into other purine nucleotides is very low.The results also support the view that 7-methylxanthine and theobromine are precursors of caffeine. For the origin of the purine ring in caffeine, purine nucleotides in the nucleotide pool rather than in nucleic acids are suggested. 相似文献
25.
J. C. Mauricio M. Pareja J. M. Ortega 《World journal of microbiology & biotechnology》1995,11(2):196-201
Significant changes in the intracellular concentrations of adenosine phosphates and nicotinamide adenine dinucleotides were observed during fermentation of grape must by three different strains ofSaccharomyces cerevisiae: S. cerevisiae var.cerevisiae, a typical fermentative yeast strain and two flor-veil-forming strains,S. cerevisiae var.bayanus andS. cerevisiae var.capensis. The intracellular concentration of ATP was always higher inS. cerevisiae var.cerevisiae than in the flor-veil-forming strains. NAD+ and NADP+ concentrations decreased at faster rates in the flor-veil-forming yeasts than in the other yeast but NADH concentration was the same in all yeasts for the first 10 days of fermentation. NADPH concentration was always lower inS. cerevisiae var.cerevisiae than in the other yeasts and this yeast also showed higher rates of growth and fermentation during the early stages of the fermentation and the presence of non-viable cells at the end of fermentation. In contrast, the flor-veil-forming strains maintained growth and fermentation capabilities for a relatively long time and viable cells were present throughout the entire fermentation process (31 days).The authors are with the Department of Microbiology, Faculty of Sciences, University of Cordoba, Avda. San Alberto Magno s/n, 14004-Córdoba, Spain 相似文献
26.
Clifford S. Morrison William B. Armiger David R. Dodds Jonathan S. Dordick Mattheos A.G. Koffas 《Biotechnology advances》2018,36(1):120-131
Industrial enzymatic reactions requiring 1,4-NAD(P)H2 to perform redox transformations often require convoluted coupled enzyme regeneration systems to regenerate 1,4-NAD(P)H2 from NAD(P) and recycle the cofactor for as many turnovers as possible. Renewed interest in recycling the cofactor via electrochemical means is motivated by the low cost of performing electrochemical reactions, easy monitoring of the reaction progress, and straightforward product recovery. However, electrochemical cofactor regeneration methods invariably produce adventitious reduced cofactor side products which result in unproductive loss of input NAD(P). We review various literature strategies for mitigating adventitious product formation by electrochemical cofactor regeneration systems, and offer insight as to how a successful electrochemical bioreactor system could be constructed to engineer efficient 1,4-NAD(P)H2-dependent enzyme reactions of interest to the industrial biocatalysis community. 相似文献
27.
J.W. Gorrod 《Chemico-biological interactions》1973,7(5):289-303
The various types of nitrogen which occur in organic compounds and which are susceptible to biological oxidation are clearly divided into groups depending upon the pKa, of the constituent nitrogen. The enzymatic processes which give rise to the N-oxidation products are reviewed by a consideration of species differences, age of animal, pH optima, influence of inducing agents, inhibitors and microsomal pretreatments, as well as the stereochemistry of the nitrogen atom.From the data collected, a concept is developed which suggests that all basic amines (group I) are oxidised by a flavine adenine nucleotide (FAD)-dependent enzyme system, whereas non-basic nitrogen-containing compounds (group III) are oxidised by a cytochrome P450-dependent system.It is further suggested that compounds of intermediary pKa,i.e. between 1 and 7 (group II), may be substrates for both enzyme systems, which would yield the same products, but by different processes. The extent to which N-oxidation occurs in a species would therefore depend on the pKa of the substrate and the amounts and ratio of the two enzymes present, a lower pKa favouring oxidation by the cytochrome P450 system and a higher pKa favouring oxidation by the FAD system.In a similar manner, it is suggested that the oxidation of aromatic heterocyclic amines depends upon the pKa of the nitrogen, compounds having a low pKa being preferentially metabolised by nitrogen oxidation. 相似文献
28.
Stella A. Child Vanessa P. Rossi Stephen G. Bell 《Biochimica et Biophysica Acta (BBA)/General Subjects》2019,1863(2):408-417
Background
Cyp147G1 is one of 47 cytochrome P450 encoding genes in Mycobacterium marinum M, a pathogenic bacterium with a high degree of sequence similarity to Mycobacterium tuberculosis and Mycobacterium ulcerans. Cyp147G1 is one of only two of these cyp genes which are closely associated with a complete electron transfer system.Methods
The substrate range of the enzyme was tested in vitro and the activity of CYP147G1 was reconstituted in vivo by co-producing the P450 with the ferredoxin and ferredoxin reductase.Results
Substrates of CYP147G1 include fatty acids ranging from octanoic to hexadecanoic acid. CYP147G1 catalysed the selective hydroxylation of linear and ω-2 methyl branched fatty acids at the ω-1 position (≥ 98%). Oxidation of ω-1 methyl branched fatty acids generated the ω and ω-1 hydroxylation products in almost equal proportions, indicating altered position of hydrogen abstraction.Conclusions
This selectivity of fatty acid hydroxylation inferred that linear species must bind in the active site of the enzyme with the terminal methyl group sequestered so that abstraction at the CH bonds of the ω-1 position is favoured. With branched substrates, one of the methyl groups must be close to the compound I oxygen atom and enable hydroxylation at the terminal methyl group to compete with the reaction at the ω-1CH bond.General significance
Hydroxy fatty acids are widely used for industrial, food and medical purposes. CYP147G1 demonstrates high regioselectivity for hydroxylation at a sub-terminal position on a broad range of linear fatty acids, not seen in other CYP enzymes. 相似文献29.
Ryo Taguchi Yo Kikuchi Yoshiyuki Sakano Tsuneo Kobayashi 《Bioscience, biotechnology, and biochemistry》2013,77(7):1583-1588
Extracellular polysaccharides produced by 3 strains of Pullularia pullulans were fractionated by treating with cetyl trimethyl ammonium hydroxide into soluble and insoluble fractions, and the structure of the former fraction, i.e., pullulan, was studied. The yield and the ratio of 2 fractions varied widely according to the strains. But the structure of pullulan was found to be uniform irrespective of the strains used. All 3 samples of pullulan gave only glucose on complete acid hydrolysis, and 93~95% maltotriose and 5~7% maltotetraose after isoamylase (pullulanase) action. The ratio of α-1,4- to α-1,6-glucosidic linkages calculated from periodate oxidation data coincided very well with the value expected from the ratio of maltotriose to maltotetraose units. An evidence for the complete absence of branch structure in pullulan was presented from the results of hydrolysis by pullulan 4-glucanohydrolase. 相似文献
30.
Pierre Andreoletti Jean-Marie Mouesca Patrice Gouet Michel Jaquinod Chantal Capeillère-Blandin Hélène Marie Jouve 《Biochimica et Biophysica Acta (BBA)/General Subjects》2009