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1.
《Comparative biochemistry and physiology. A, Comparative physiology》1979,62(4):939-945
- 1.1. Myo-inositol is transported in chicken small intestine by a mediated route with an apparent Km of 0.1 mM and by a diffusion mechanism.
- 2.2. The mediated route is susceptible to inhibition by sugars, though sugars are not transported by this process, nor is myo-inositol transported by the sugar transport system.
- 3.3. Myo-inositol influx is inhibitable by phlorizin, sulfhydryl reagents, removal of Na+ from the incubation medium, and preloaded sugar; it can be stimulated by theophylline.
- 4.4. The ability to absorb this nutrient varies greatly between individual animals.
2.
The present study investigates the effects of indole-3-butyric acid (IBA) alone and in combination with myo-inositol on in vitro rooting and biochemical responses in the cherry rootstocks CAB-6P (Prunus cerasus L.) and Gisela 6 (Prunus cerasus × Prunus canescens). For the CAB-6P rootstock, the best results for root number (6.31), fresh mass (FM), dry mass (DM), and rooting percentage (100 %) were obtained on Murashige and Skoog (MS) medium with 2 mg dm?3 IBA and maximum root length (30.57 mm) was obtained at 1 mg dm?3 IBA. Myo-inositol suppressed the positive effects of IBA on root length. In the Gisela 6 explants, the inclusion of 2 mg dm?3 IBA together with 0.5 mg dm?3 of myo-inositol in the culture medium significantly enhanced root number (9.91) and root FM and DM. The root length was maximum in the combination of the lowest IBA and myo-inositol concentrations (0.5 mg dm?3). The rooting percentage was the greatest (100 %) with the application of 1 mg dm?3 IBA alone. In both explants, the application of IBA alone or in combination with myo-inositol resulted in a lower leaf proline content in comparison with the control (without growth regulators). The maximum leaf chlorophyll content was at 1 mg dm?3 IBA in the CAB-6P whereas at 2 mg dm?3 IBA and 1 mg dm?3 myo-inositol in Gisela 6. Addition of myo-inositol mostly increased sugar content in comparison with control or IBA alone in both rootstocks. 相似文献
3.
A novel enzyme, myo-inositol-1-phosphate dehydrogenase, which catalyzes the conversion of myo-inositol 1-phosphate to ribulose 5-phosphate has been purified 84-fold from mung bean seedling employing several common techniques. The molecular weight of this purified enzyme has been recorded as 88,500 by Sephadex G-200 column chromatography, and in sodium dodecyl sulfate-polyacrylamide gel electrophoresis one protein band containing three subunits of Mr 32,000 each was discernible. Km values for NAD+ and myo-inositol 1-phosphate have been recorded as 2.8 × 10?4 and 5.0 × 10?4m, respectively. Production of NADH in myo-inositol-1-phosphate dehydrogenase reaction has also been evidenced by measurement of NADH fluorescence. Dehydrogenation and decarboxylation of myo-inositol 1-phosphate are mediated by the same enzyme. In fact, the rate of dehydrogenation corroborates with that of decarboxylation. Stoichiometry of this reaction suggests that for the production of 1 mol of ribulose 5-phosphate 2 mol of NAD+ are reduced. 相似文献
4.
We optimized the conditions for isolation of extracellular catalases from Penicillium piceum F-648 and P. piceum A3 by means of volume chromatography with cadmium hydroxide gel. Our study showed that 55–57 mg wet gel are sufficient for the maximum sorption of catalase from 1 ml of culture fluid. This gel was formed in 1 ml 70 mM Cd(NO3)2 after addition of NaOH (Cd(NO3)2/NaOH molar ratio 1: 2.2). The eluting solution contained 50 mM NaH2PO4(pH 7.0), 5.0 mM dithiothreitol, and 0.3% sodium cholate and was potent in desorbing catalase from the gel. Subsequent ultrafiltration of the eluate on the membrane with a retention limit of 50 kDa allowed us to concentrate and purify the sample from low-molecular-weight protein impurities. NH4Cl (1.0 M) containing 0.3% sodium cholate was used to wash the sample from low-molecular-weight aromatic metabolites. Purified catalases included 33–34% antiparallel β-structures and 9%-spirals. Under optimal conditions in the medium of 10 mM phosphate buffered saline (pH 7.0) at 30°C, catalases from P. piceum F-648 were characterized by the following parameters: K M, 158.8 mM; catalytic constant, 2.83 × 106 s?1; enzyme inactivation rate constant in H2O2 decomposition, 3.5 × 10?2 s?1; and constant of the interaction between catalase complex I and second molecule of H2O2, 1.8 × 107M?1 s?1. 相似文献
5.
(1) Unidirectional K+ (86Rb) influx and efflux were measured in subconfluent layers of MDCK renal epithelial cells and HeLa carcinoma cells. (2) In both MDCK and HeLa cells, the furosemide-inhibitable and chloride-dependent component of K+ influx/efflux was stimulated 2-fold by a 30 min incubation in 1 · 10?3 M ouabain. (3) Measurements of net K+ loss and Na+ gain in ouabain-treated cells at 1 h failed to show any diuretic sensitive component, confirming the exchange character of the diuretic-sensitive fluxes. (4) Prolonged incubations for 2.5 h in ouabain revealed a furosemide- and anion-dependent K+ (Cl?) outward net flux uncoupled from net Na+ movement. Net K+ (Cl?) outward flux was half-maximally inhibited by 2 μM furosemide. (5) After 2.5 h ouabain treatment, the anion and cation dependence of the diuretic-sensitive K+ influx/efflux were essentially unchanged when compared to untreated controls. 相似文献
6.
《Life sciences》1995,57(5):PL71-PL74
The effects of elevated glucose and eicosapentaenoic acid (EPA, C20:5 ω3) on myo-inositol uptake in human skin fibroblasts (HSF) were evaluated. Myo-inositol incorporation into HSF was dependent on an active transport system via Na+-K+ ATPase activity based on the results with Na+ deprivation and ouabain (5 mM). Although glucose (27.5, 55 mM) inhibited 2-[3H] myo-inositol uptake, the addition of EPA (3×10−4M) prevented glucose-mediated inhibition. Since EPA decreased glucose-mediated inhibition of myo-inositol uptake, this agent might ameliorate some of the devastating functions associated with diabetes. 相似文献
7.
T Araiso H B Dunford C K Chang 《Biochemical and biophysical research communications》1979,90(2):520-524
Recombination of apo horseradish peroxidase with 2,4 dimethyldeutero hemin and its mono- and dimethyl esters was performed. The number of free carboxyl side chains in these three hemins is 2, 1 and 0 respectively. Despite such a difference, all of these three reconstituted enzymes can react with H2O2 to produce compound I. The second order rate constants for compound I formation are 1.3 × 107 M?1s?1, 8.5 × 106 M?1s?1 and 5.9 × 106 M?1s?1. Therefore the propionate side chain of hemin has no direct role in compound I formation. 相似文献
8.
Uptake of 14C-labelled sucrose and glucose by isolated seed coat halves of pea (Pisum sativum L. cv. Marzia) seeds was measured in the concentration range <0.1 μM to 100 mM. The initial influx of sucrose was strictly proportional to the external concentration, with a coefficient of proportionality (k) of 6.2 μmol·(g FW)?1·min?1·M?1. Sucrose influx was not affected by 10 μM carbonylcyanide m-chlorophenylhydrazone (CCCP), but it was inhibited by 40% in the presence of 2.5 mM p-chloromercuribenzenesulfonic acid (PCMBS). Influx with diffusional kinetics was also observed for glucose (k = 4.8 μmol·(g FW)?1·min ?1·M ?1) and mannitol (k = 5.1 μmol·(g FW)?1·min?1·M?1). For glucose an additional saturable system was found (Km = 0.26 mM, V max = 4.2 nmol·(g FW)?1·min?1), which appeared to be completely inhibited by CCCP and partly by PCMBS. In contrast to the diffusional pathway, uptake by this saturable system was slightly pH-dependent, with an optimum at pH 5.5. The influx of sucrose appears to be by the same pathway as the efflux of endogenous sucrose, which was inhibited by 36% in the presence of 2.5 mM PCMBS (De Jong A, Wolswinkel P, 1995, Physiol Plant 94: 78–86). It is argued that passive transport may be the only mechanism for sucrose transport through the plasma membrane of seed coat parenchyma cells. The estimated permeability coefficient of the plasma membrane for sucrose (P = 3.5·10?7 cm·s?1) is more than 1 × 106-fold higher than that reported for artificial lipid membranes. This relatively high permeability is hypothesized to result from pore-forming proteins that allow the diffusion of sucrose. Furthermore, it is shown that a sucrose gradient across the plasma membrane of the seed coat parenchyma of only 22 mM will suffice to result in the net efflux of sucrose which is required to feed the embryo. 相似文献
9.
PIRJO KARUNEN 《Physiologia plantarum》1979,45(2):197-200
The dry matter production in Polytrichum commune protonemata was increased when the light intensity was increased from 0 to 160 μE m?2 s?1, and at 160 μE m?2 s?1 production was about 200% of that found at 17 μE m?2 s?1. Production of chlorophyll (Chl) was increased by increasing light intensity from 0 to 17 μE m?2 s?1, but decreasing at light intensities above 17 μE m?2 s?1. At 160 μE m?2 s?1 the production of Chl was only about 50% of that at 17 μE m?2 s?1. The rate of CO2 fixation was low (0.31 μg CO2/mg Chi × h) at the light intensity of 17 μE m?2 s?1 as compared with that at 160 μE m?2 s?1 (0.83 μg CO2/mg Chi × h). Production of mono- (MGDG) and diglycosyl diglycerides (DGDG) was closely associated with that of chlorophylls. At the higher light intensity (160 μE m?2 s?1) production of glycolipids was about 60% of that at 17 μE m?2 s?1. Production of more polar lipids was less affected by light intensity. Light intensity also affected the fatty acid pattern of the lipid fractions. The effect was most pronounced in the MGDG fraction, where the proportion of C 18: 3ω3 + C 16: 3ω3 was higher at the higher light intensity. 相似文献
10.
The permeability of biological membranes to boric acid was investigated using the giant internodal cells of the charophyte
alga Chara corallina (Klein ex Will. Esk. R.D. Wood). The advantage of this system is that it is possible to distinguish between membrane transport
of boron (B) and complexing of B by plant cell walls. Influx of B was found to be rapid, with equilibrium between the intracellular
and extracellular phases being established after approximately 24 h when the external concentration was 50 μM. The intracellular
concentration at equilibrium was 55 μM, which is consistent with passive distribution of B across the membrane along with
a small amount of internal complexation. Efflux of B occurred with a similar half-time to influx, approximately 3 h, which
indicates that the intracellular B was not tightly complexed. The concentration dependence of short-term influx measured with
10B-enriched boric acid was biphasic. This was tentatively attributed to the operation of two separate transport systems, a
facilitated system that saturates at 5 μM, and a linear component due to simple diffusion of B through the membrane. V
max and K
m for the facilitated transport system were 135 pmol m−2 s−1 and 2 μM, respectively. The permeability coefficient for boric acid in the Chara plasmalemma estimated from the slope of the linear influx component was 4.4 × 10−7 cm s−1 which is an order of magnitude lower than computed from the ether:water partition coefficient for B.
Received: 14 August 2000 / Accepted: 16 September 2000 相似文献
11.
Hydrogen peroxide amplifies the chemiluminescence in the oxidation of luminol by sodium hypochlorite. A linear relationship between concentration of hydrogen peroxide and light intensity was found in the concentration range 5 × 10?8?7.5 × 10?6 mol/l. At 7.5 × 10?6 mol/l H2O2 the chemiluminescence is amplified 550—fold. The chemiluminescence spectra of these reactions have a wavelength maximum at 431 nm independent of the concentration of hydrogen peroxide. The results indicate that hydrogen peroxide is a necessary component in the chemiluminescent oxidation of the luminol by sodium hypochlorite. 相似文献
12.
P18, the sole component of T4 tail sheath, has been isolated in a monomeric active form from extended sheaths of intact tails which were dissociated at low ionic strength. The molecular weight of P18 is determined to be 65,000 from sedimentation equilibrium and 73,000 from sodium dodecyl sulphate/gel electrophoresis. Combining the diffusion constant (D20,w = 5·5× 10?7cm2s?1)and the sedimentation constant (s020,w = 4·2 S) a value of 67,000 is obtained. The circular dichroism spectra reveal a striking similarity of the structure of P18 in the monomeric state and in the extended sheath conformation.The purified P18 is found to reassemble into extended sheaths if the core-baseplate complex is present, forming normal length tails. Structures similar to polysheath are formed in the absence of core-baseplates. 相似文献
13.
Furosemide () inhibits a proportion of the total passive (ouabain-insensitive) K+ influx into primary chick heart cell cultures (85%), BC3H1 cells (75%), MDCK cells (40%) and HeLa cells (57%). This action of furosemide upon K+ influx is independent of ( inhibition since the furosemide-sensitive component of the K+ influx is identical in the presence and absence of ouabain (). For HeLa cells the passive, furosemide-sensitive component of K+ influx is markedly dependent upon the external K+, Na+ and Cl? content. Acetate, iodide and nitrate are ineffective as substitutes for Cl?, whereas Br? is partially effective. Partial Cl? replacement by NO3? gave an apparent affinity of 100 mM [Cl]. Na+ replacement by choline+ abolishes the furosemide-sensitive component, whereas Li+ replacement reduces this component by 48%. Partial Na+ replacement by choline+ gives an apparent affinity of 25 mM [Na+]. Variation in the external K+ content gives an affinity for the furosemide-sensitive component of approx. 1.0 mM. Furosemide inhibition of the passive K+ inflúx is of high affinity, half-maximal inhibition being observed at furosemide. Piretanide () and phloretin () inhibit the same component of passive K+ influx as furosemide; ethacrynic acid and amiloride () partially so. The stilbene, SITS (), was ineffective as an inhibitor of the furosemide-sensitive component. 相似文献
14.
P. K. Chaurasia A. Yadav R. S. S. Yadav S. Yadava 《Applied Biochemistry and Microbiology》2013,49(6):592-599
A laccase from the culture filtrate of Phellinus linteus MTCC-1175 has been purified to homogeneity. The method involved concentration of the culture filtrate by ammonium sulphate precipitation and an anion exchange chromatography on DEAE-cellulose. The SDS-PAGE and native-PAGE gave single protein band indicating that the enzyme preparation was pure. The molecular mass of the enzyme determined from SDS-PAGE analysis was 70 kDa. Using 2.6-dimethoxyphenol, 2.2′[azino-bis-(3-ethylbonzthiazoline-6-sulphonic acid) diammonium salt] (ABTS) and 4-hydroxy-3,5-dimethoxybenzaldehyde azine as the substrates, the K m, k cat and k cat/K m values of the laccase were found to be 160 μM, 6.85 s?1, 4.28 × 104 M?1 s?1, 42 μM, 6.85 s?1, 16.3 × 104 M?1 s?1 and 92 μM, 6.85 s?1, 7.44 × 104 M?1 s?1, respectively. The pH and the temperature optima of the P. linteus MTCC-1175 laccase were 5.0 and 45°C, respectively. The activation energy for thermal denaturation of the enzyme was 38.20 kJ/mole/K. The enzyme was the most stable at pH 5.0 after 1 h reaction. In the presence of ABTS as the mediator, the enzyme transformed toluene, 3-nitrotoluene and 4-chlorotoluene to benzaldehyde, 3-nitrobenzaldehyde and 4-chlorobenzaldehyde, respectively. 相似文献
15.
The effects of extracellular Pi and Na+ on cellular Pi concentration and transport were studied. Steady-state Pi exchange flux was measured by 32P uptake in the presence and absence of Na+. Model experiments were also conducted to assess the possibility that hydrolysis of organic phosphate esters contributes to the chemically measured intracellular Pi concentration of Ehrlich ascites tumor cells. The results of these experiments indicate that hydroloysis of labile organic phosphate esters does not contribute to the measured intracellular pool of Pi. The Pi transport system exhibits an apparent Ks of 0.115 mM Pi and a maximal flux of 1.73 mmole min?1 (kg dry wt)?1. When incubated in a phosphate-buffered choline chloride medium (5 mM Pi) the intracellular Pi and the Pi influx fall by 65 and 88%, respectively. At 5 mM extracellular Pi, the Na+-dependent component of Pi transport fits Michaelis-Menten kinetics with the maximal flux equal to 2.46 mmole min?1 (kg dry wt)?1 and an apparent Ks of 35.4 mM Na+. In addition, a Na+-independent component of Pi transport, comprising about 12% of the total Pi flux, was identified. The data support the hypothesis that a Pi transport system, dependent on Na+, plays a principal role in the maintenance of intracellular Pi concentration. 相似文献
16.
Background and aims
Accumulation of Cd in the shoots of plants grown on Cd contaminated soils shows considerable variation. A previous preliminary experiment established that one major reason for this variation was the rate of Cd influx into the roots (mol Cd cm?2 root s?1). However, this experiment did not distinguish between solubilization of soil Cd on the one hand and difference in Cd uptake kinetics on the other. The main objectives of the present study were thus to characterize Cd uptake kinetics of plants continuously exposed to Cd concentrations similar to those encountered in soils. Furthermore we determined the factors responsible for differences in shoot Cd concentration such as net Cd influx, root area-shoot dry weight ratio, shoot growth rate and proportion of Cd translocated to the shoot.Materials and methods
Maize, sunflower, flax and spinach were grown in nutrient solution with five constant Cd concentrations varying from 0 to 1.0 μmol?L?1. Root and shoot parameters as well as Cd uptake were determined at two harvest dates and from these data Cd net influx and shoot growth rates were calculated.Results and conclusions
Cadmium uptake kinetics, i.e. the net Cd influx vs. Cd solution concentration followed a straight line. Its slope is the root absorbing power, α, $ \left( {\alpha ={{{\mathrm{Cd}\;\mathrm{net}\;\mathrm{influx}}} \left/ {{\mathrm{Cd}\;\mathrm{solution}\;\mathrm{concentration}}} \right.}} \right) $ . The α values of spinach and flax were about double that of maize and sunflower (5?×?10?6?cm?s?1 vs. 2.5?×?10?6?cm?s?1). Spinach and flax had a 3–5 times higher shoot Cd concentration than maize and sunflower. The difference in shoot Cd concentration was partly due to the higher Cd influx but also to a higher translocation of Cd from root to shoot and also to a slower shoot growth rate. 相似文献17.
Summary Maximum growth of suspension cultures of Paul's Scarlet rose has been demonstrated in a minimal organic medium possessing only 4 organic compounds: napthaleneacetic acid, kinetin, myo-inositol, and sucrose. Myo-inositol was not essential for growth, but sustained growth was reduced by 90% when it was omitted. Maximum growth required nitrate plus a supplemental amount of either NH
4
+
or glutamine. 相似文献
18.
Abstract: Pridefine (AHR-1118) is a pyrrolidine derivative with clinically established antidepressant efficacy. Previous work from this laboratory indicates that pridefine is a reuptake blocker of catecholamines and serotonin with weak releasing activity. This study characterized the mode of amine uptake inhibition by pridefine as noncompetitive. The uptake experiments were performed utilizing ouabain instead of zero-degree controls to differentiate between the passive and active components of uptake. Furthermore, the passive component was resolved into diffusion and binding of substrate. Correction was made for the effects of ouabain on binding. Kinetic constants determined from Lineweaver-Burk plots were: Km= 3 × 10?7 M for NE, Km= 9 × 10?8 M for DA, and Km= 3 × 10?8 M for 5-HT. Dixon analyses of uptake at various pridefine concentrations indicated noncompetitive inhibition with Ki= 2.5 × 10?6 M for NE uptake, Ki= 2.0 × 10?6 M for DA uptake, and Ki= 1 × 10?5 M for 5-HT uptake. These constants compare well with IC50 values for the same transmitters: NE, IC50= 2.4 × 10?6 M; DA, IC50= 2.8 × 10?6 M; 5-HT, IC50= 1.0 × 10?5 M. The in vitro results indicate that pridefine is relatively specific as a catecholamine uptake blocker. It differs from tricyclic antidepressants which are reportedly competitive inhibitors of monoamine uptake. The possible mechanisms by which pridefine acts as a noncompetitive inhibitor are discussed. 相似文献
19.
20.
The translational and rotational dynamics of tobacco mosaic virus in sodium phosphate buffer (pH =7.5) solutions has been investigated by polarized and depolarized light scattering Rayleigh linewidth studies. For concentrations ranging from 1.75 × 10?4 g ml?1 to 0.25 × 10?4 g ml?1 the translational diffusion coefficient (DT) has been found to be slightly concentration dependent and extrapolation to zero concentration gives D020°C = 0.34 ± 0.01 × 10?7 cm2S?1. A full analysis of the polarized spectra obtained at high and low scattering angles and the depolarized spectra at near zero scattering angles has enabled these techniques to be compared and the rotational diffusion constant DR to be determined. At a solution concentration of 1.75 × 10?4 g ml?1 a mean value is found to be DR20°C = 350 ± 30s?1. These values of DT and DR are in approximate agreement with calculations based on models of the tobacco mosaic virus molecule as a cylindrical rod. 相似文献