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The steady-state kinetics of isotope exchange for one substrate–one product enzymic reactions
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Ivan G. Darvey 《The Biochemical journal》1973,135(4):861-866
Steady-state kinetic equations for isotope exchange are derived for a number of one substrate-one product enzymic mechanisms in which two molecules of substrate or product can be combined with an enzyme molecule at the one time (e.g. allosteric mechanisms). The usual assumption, that the radioactive material is distributed among the substrate and product components according to a first-order law, is not valid. One can recognize whether isotope-exchange kinetics of an enzyme reaction follows first-order behaviour by using various initial concentrations of the labelled substance added to a mixture. 相似文献
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Ivan G. Darvey 《The Biochemical journal》1974,143(3):783-784
The conclusion that the steady-state kinetics of isotope exchange at equilibrium do not show first-order behaviour for some one substrate-one product enzymic mechanisms in which two molecules of substrate or product can be combined with an enzyme molecule at the one time was shown to be erroneous. 相似文献
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Tarne Peter Lehmann Annekatrin Kantner Michael Finkbeiner Matthias 《The International Journal of Life Cycle Assessment》2019,24(8):1461-1479
The International Journal of Life Cycle Assessment - Product sustainability assessment should evaluate the impacts on all three dimensions of sustainability (environment, economy, and society).... 相似文献
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Oxysterols are potent signalling lipids that directly bind liver X receptors (LXRs) and a subset of oxysterol binding protein (OSBP) related proteins (ORPs). It is relatively well established that the oxysterol-regulated function of LXRs is to control the expression of genes involved in reverse cholesterol transport, catabolism of cholesterol, and lipogenesis. In contrast, the mechanisms by which oxysterols and ORPs affect cellular lipid metabolism have remained poorly understood. In this review, we summarize the information available on function of the ORPs and compare the two families of proteins binding oxysterol to demonstrate the different responses that similar lipids can elicit within cells. The other focus is on the membrane targeting determinants and the protein interaction partners of ORPs, which provide interesting clues to the mode(s) of ORP action. Specifically, we suggest a model in which a general property of ORPs is to function at membrane contact sites, specialized zones of communication between two different organelles. 相似文献
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Furnham N Blundell TL DePristo MA Terwilliger TC 《Nature structural & molecular biology》2006,13(3):184-5; discussion 185
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Wigley DB 《Current biology : CB》2000,10(12):R444-R446
One might imagine that the mechanism of helicases would relate to the number of base pairs that are unwound for each ATP that is hydrolysed. Recent studies, however, suggest the situation can be more complicated than this. 相似文献
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Subliminal words cause behavioral priming, yet the depth of their processing remains debated. Using transcranial magnetic stimulation (TMS), Nakamura et al. demonstrate in this issue of Neuron that this subliminal priming effect can be selectively disrupted. Distinct TMS sites disrupt priming in lexical decision and pronunciation tasks, suggesting that task set influences subliminal processing. 相似文献
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Maurizio Bevilacqua Ligia J. Dominguez Giorgio Gandolini Valeria Valdes Tarcisio Vago Velella Righini Massimo Barrella Mario Barbagallo 《The Journal of steroid biochemistry and molecular biology》2009,113(1-2):3-8
Absorptive hypercalciuria (AH) is associated with elevated levels of 1,25-dihydroxyvitamin D (1,25(OH)2D). While no increase of 1,25(OH)2D after oral administration of 25-hydroxyvitamin D (25OHD) at high doses has been claimed in normal subjects, a substrate–product relationship has been reported in normal children, young people after UV irradiation, older persons, postmenopausal women, primary hyperparathyroidism, renal failure, osteomalacia, and sarcoidosis. No data of this relationship in AH is available. To investigate 25OHD-1,25(OH)2D substrate–product relationship in AH, 161 AH patients (mean age 60.9 ± 11.7 years) and 110 age- and sex-matched controls (mean age 61.5 ± 12.4 years) were studied. In 57 controls and 52 AH subjects 25OHD-1,25(OH)2D relationship in basal conditions and after 2-week oral 25OHD (25 μg/day) administration were evaluated. In basal conditions 25OHD and 1,25(OH)2D were correlated in both, controls and AH; 25OHD treatment was followed by an increase in serum 25OHD and 1,25(OH)2D in both groups. However, delta responses of 25OHD and 1,25(OH)2D to 25OHD were higher in AH suggesting an enhanced activity of 1α-hydroxylase. In conclusion, the higher response of 1,25(OH)2D after oral 25OHD in AH patients suggests a differential capacity between both groups in handling the increases in 1,25(OH)2D. 相似文献
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Sucrose or trehalose at 0.3 M stabilised double-stranded DNA in PCR. Furthermore, the DNA polymerase from Thermus aquaticus was stabilised towards thermo-denaturation at 98°C by sucrose or trehalose. The effect was limited to these sugars and was shown not to be general for carbohydrates. 相似文献
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《Bioorganic & medicinal chemistry letters》2014,24(5):1432-1436
d-Glutamate is an essential biosynthetic building block of the peptidoglycans that encapsulate the bacterial cell wall. Glutamate racemase catalyzes the reversible formation of d-glutamate from l-glutamate and, hence, the enzyme is a potential therapeutic target. We show that the novel cyclic substrate–product analogue (R,S)-1-hydroxy-1-oxo-4-amino-4-carboxyphosphorinane is a modest, partial noncompetitive inhibitor of glutamate racemase from Fusobacterium nucleatum (FnGR), a pathogen responsible, in part, for periodontal disease and colorectal cancer (Ki = 3.1 ± 0.6 mM, cf. Km = 1.41 ± 0.06 mM). The cyclic substrate–product analogue (R,S)-4-amino-4-carboxy-1,1-dioxotetrahydro-thiopyran was a weak inhibitor, giving only ∼30% inhibition at a concentration of 40 mM. The related cyclic substrate–product analogue 1,1-dioxo-tetrahydrothiopyran-4-one was a cooperative mixed-type inhibitor of FnGR (Ki = 18.4 ± 1.2 mM), while linear analogues were only weak inhibitors of the enzyme. For glutamate racemase, mimicking the structure of both enantiomeric substrates (substrate–product analogues) serves as a useful design strategy for developing inhibitors. The new cyclic compounds developed in the present study may serve as potential lead compounds for further development. 相似文献
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A. V. LeBouton 《The Biochemical journal》1968,106(2):503-506
Rats were injected with [(3)H]leucine, and at various times thereafter labelled albumin was isolated by electrophoresis from their livers and blood plasma. The specific radioactivity of each protein was determined by spectrophotometry and liquid-scintillation spectrometry. Intrahepatic albumin was shown to be identical with plasma albumin by its electrophoretic mobility and antigenicity. It was found that intrahepatic albumin was the direct precursor of plasma albumin. Comparison of their specific radioactivities showed that intrahepatic albumin attained a higher specific radioactivity before plasma albumin. When plasma albumin reached its maximum specific radioactivity, that of intrahepatic albumin had decreased to a similar value. Thereafter, the specific radioactivity of intrahepatic albumin remained lower than that of plasma albumin. 相似文献
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A number of medical specialties have recently developed their own specialty-specific charters. This proliferation of charters is representative of an unease about medical professionalism that has arisen not just from increasing medical specialization, but also from evolving needs as physicians progress through their careers. The development of such specialty-specific definitions of professionalism is undesirable: all specialties should adhere to the same basic principles. These charters and "definitions" should be incorporated into a formal developmental model, derived from needs assessments from the level of medical school through the level of specialization. Such a model would provide physicians with more concrete guidance regarding professional behavior at each stage of their careers, address unmet needs in neglected areas such as mid- and late career, and help alleviate the tension associated with expressing these ideas. Incorporating concepts derived from more classic models of development may create opportunities to address the teaching of values and identify barriers to success. 相似文献
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Summary The purpose of this work was to study some biochemical and microbiological changes occurring during the fermentation of chorote, an important indigenous fermented food in the Mexican state of Tabasco. The chorote solid state fermentation is similar to that for the production of pozol, though fermented and roasted cacao beans are added to the maize dough. Changes in pH, lactic acid, total and soluble protein, available lysine and tryptophan as well as in some microbial groups were recorded during a 9-day fermentation period. Microbiological analysis showed an increase in moulds, yeasts, amylolytic lactic acid and nitrogen-fixing bacteria during the fermentation. There was a decrease in pH (to 4.2) and a significant net increase in protein content. There was also an increase in soluble protein and tryptophan. 相似文献
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Brandon Kuczenski Antonino Marvuglia Miguel F. Astudillo Wesley W. Ingwersen M. Barclay Satterfield David P. Evers Christoph Koffler Tomás Navarrete Ben Amor Lise Laurin 《The International Journal of Life Cycle Assessment》2018,23(8):1685-1692