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1.
Tsang PW 《Mycopathologia》2011,172(6):473-479
The present study was undertaken to evaluate and characterize the phytase activity in different Candida species. A total of 113 Candida isolates representing eight species were examined for phytase activity by an agar plate assay using the calcium salt of phytic acid as the sole phosphorus source. A phytase-positive phenotype was identified by the formation of a clear halo around a fungal colony. Cell-bound differential phytase activity was observed in Candida isolates at inter- and intra-species levels. Although phytase activity was not affected by the supplementation of external phosphate in C. albicans, C. dubliniensis, C. glabrata, and C. kefyr, elevated phytase activity was evident in C. guilliermondii, C. krusei, C. parapsilosis, and C. tropicalis in phosphate-free medium. Further characterization showed that, in general, relatively higher phytase activity was observed at more acidic pHs, and the phytase activity increased with incubation temperature, reaching a maximum at 55 or 65°C. Taken together, the findings demonstrated, for the first time, differential phytase activities in different Candida species. Phytase activity may be a contributing factor to fungal survival and proliferation within the human gastrointestinal tract, where nutrients are usually scarce.  相似文献   

2.
Aims: The aim of this study was to select and examine Saccharomyces and Brettanomyces brewing yeasts for hydrolase activity towards glycosidically bound volatile compounds. Methods and Results: A screening for glucoside hydrolase activity of 58 brewing yeasts belonging to the genera Saccharomyces and Brettanomyces was performed. The studied Saccharomyces brewing yeasts did not show 1,4‐β‐glucosidase activity, but a strain dependent β‐glucanase activity was observed. Some Brettanomyces species did show 1,4‐β‐glucosidase activity. The highest constitutive activity was found in Brettanomyces custersii. For the most interesting strains the substrate specificity was studied and their activity was evaluated in fermentation experiments with added hop glycosides. Fermentations with Br. custersii led to the highest release of aglycones. Conclusions: Pronounced exo‐β‐glucanase activity in Saccharomyces brewing yeasts leads to a higher release of certain aglycones. Certain Brettanomyces brewing yeasts, however, are more interesting for hydrolysis of glycosidically bound volatiles of hops. Significance and Impact of the Study: The release of flavour active compounds from hop glycosides opens perspectives for the bioflavouring and product diversification of beverages like beer. The release can be enhanced by using Saccharomyces strains with high exo‐β‐glucanase activity. Higher activities can be found in Brettanomyces species with β‐glucosidase activity.  相似文献   

3.
The activity of extracted NADH-NO3? reductase was measured in the marine dinoflagellates Amphidinium carteri Hulburt and Cachonina niei Loeblich. Its activity showed a diel periodicity and was ca. twice as great at midday as at midnight. The enzyme activity was unstable, with an in vitro half-life of 2–3 h. Values of enzyme activity were low or undetectable during lag phase but paralleled the instantaneous growth rate value during log phase. Nitrate reductase activity was not found in the stationary phase of growth, but additions of NO3? resulted in enzyme activity after 24h. When A. carteri was exposed to a series of light intensities for several weeks, the division rate and enzyme activity increased with increasing light intensity up to saturating intensities. In 6 h exposures, enzyme activity decreased with decreasing light intensities below light intensities saturating division rate. Additions of NH4+ (0.5–50 μm) to A. carteri cultures decreased the amount of extractable enzyme. The in vitro activity was not inhibited by similar NH+4 concentrations.  相似文献   

4.
Plant defence mechanisms can reduce the digestive enzyme activity of insect pests. The aim of this study was to determine the relationship between the production of proteinase inhibitors, lipoxygenase and polyphenol oxidase activity in Coffea arabica (Catuai IAC 15) plants, and the digestive enzyme activity in the pest Leucoptera coffeella (Lepidoptera: Lyonetiidae) after feeding on the plant. The production of proteinase inhibitors was evaluated with L‐BApNA as a substrate. We studied lipoxygenase activity with linoleic acid and polyphenol oxidase activity with catechol substrates, in coffee plants damaged (T1) and not damaged (T2) by L. coffeella. L. coffeella digestive enzyme activity was verified by trypsinlike (substrate l ‐BApNA and l ‐TAME), chymotrypsinlike (BTpNA and ATEE), cysteine proteases (l ‐BApNA) and total protease (azocasein). Proteinase inhibitor production and lipoxygenase and polyphenol oxidase activity in C. arabica increases (P ≤ 0.05) with L. coffeella damage. Our results provide important information that these enzymatic activities may play a role in plant defence processes in C. arabica. Trypsinlike activity increases, whereas chymotrypsin‐like and cysteine protease activity decrease in the midgut of L. coffeella, which acts as a defence mechanism.  相似文献   

5.
Summary Our previous experiments on maize (Zea mays L.) plants regenerated from tissue culture revealed genetic activity characteristic of the transposable element Activator (Ac) in the progeny of 2–3% of the plants tested, despite the lack of Ac activity in the progenitor plants. The objective of the present study was to determine whether the presence of Ac activity in tissue-culture-derived plants was associated with changes in the number or structure of Ac-homologous DNA sequences. Families segregating for Ac activity were obtained by crossing plants heterozygous for Ac activity onto Ac-responsive tester plants. A DNA probe derived from a previously isolated Ac sequence was used to examine the Ac-homologous sequences within individual progeny seedlings of segregating families and noncultured control materials. All plants tested had six or more Ac-homologous DNA sequences, regardless of whether Ac activity was present. In the segregating progeny of one tissue-culturederived plant, a 30-kb Ac-homologous SstI restriction fragment and a 10-kb Ac-homologous BglII restriction fragment were found to cosegregate with Ac activity. We propose that these fragments contained a previously silent Ac sequence that had been activated during tissue culture. Although one or more Ac sequences were often hypomethylated at internal PvuII and HpaII sites in plants with Ac activity, hypomethylation was not a prerequisite for activity. Reduced methylation at these sites may have been a result rather than a cause of Ac activity.  相似文献   

6.
The effect of 20-hydroxyecdysone (20E) and the juvenile hormone (JH) on the activity of the arylalkylamine N-acetyltransferase (AANAT) was studied in young females of wild-type D. virilis and D. melanogaster. 20E feeding of the flies led to a decrease in AANAT activity in both species when dopamine (DA) was used as substrate, but did not affect the enzyme activity when octopamine (OA) was used as substrate. JH application increased AANAT activity with DA as substrate in both species, but did not change it with OA as substrate. AANAT activity was also measured in young females of a JH-deficient strain of D. melanogaster, apterous 56f . A decrease in the enzyme activity was observed in the mutant females as compared to wild-type. Mechanisms of regulation of DA level by gonadotropins in Drosophila are discussed.  相似文献   

7.
Seven seaweeds were collected from the intertidal zone at Rocky Bay on the east coast of South Africa. The species were Caulerpa racemosa var. laetevirens, Codium capitatum, Halimeda cuneata, Ulva fasciata, Amphiroa bowerbankii, Amphiroa ephedraea and Dictyota humifusa. Six bimonthly collections were made within a few days of the new moon to correspond with spring tide. Methanol extracts were tested for antifungal, antibacterial and acetylcholinesterase (AChE) inhibitory activity. No seasonal variation was observed in antifungal activity, with D. humifusa extracts being the most active. The seaweed extracts inhibited the growth of the Gram-positive bacteria, with Bacillus subtilis being more susceptible than Staphylococcus aureus. Dictyota humifusa was the only seaweed able to inhibit the Gram-negative Escherichia coli. Seasonal variation in antibacterial activity was observed, with the extracts generally having no activity in summer and having antibacterial activity in late winter (July collection) and early spring (September and November collections). Dictyota humifusa was the most effective seaweed species, having antibacterial activity throughout the year. All the extracts tested had AChE inhibitory activity, with no seasonal variation in the levels of activity. Dictyota humifusa extracts were the most effective at inhibiting AChE activity.  相似文献   

8.
The response of glycolate oxidase from shoots of Salicornia europaea L. and from leaves of Pisum sativum L. to salt treatment during assay was studied by DCPIP reduction and O2 uptake. In Pisum there was found up to five times more glycolate oxidase activity per gram fresh weight than in Salicornia. However, the calculation of the specific activity pointed out that this result was caused only by the high level of enzyme protein in Pisum, and that specific activity from both species was of equal size. By the DCPIP method it was shown that in test media containing up to 1.0 M NaCl or KCl glycolate oxidase of Salicornia was of equal size compared with the control (medium without additional salts). With 2.0 M NaCl or KCl the activity decreased by about 80 and 30% respectively. Glycolate oxidase of Pisum was somewhat more salt sensitive. 1.0 M NaCl or KCl reduced the activity by about 35%. In the presence of 2.0 M NaCl or KCl the enzyme activity from Pisum was inhibited to about 80 and 60% respectively. By substituting sulfates for chlorides the activity of glycolate oxidase from both Salicornia and Pisum was stimulated strongly. 1.5 M Na2SO4 and 0.5 M K2SO4 (both are saturated solutions) caused an increase of glycolate activity from Salicornia of about 225 and 185% respectively, and from Pisum of about 50 and 30% respectively. Studying the response of glycolate oxidase to salt treatment by O2 uptake one must establish that with this method the degree of inhibition of enzyme activity at higher salt concentrations was always more severe than with dye reduction. Addition of 1.0 M NaCl or KCl to the assay medium caused an inhibition of glycolate oxidase activity from Salicornia of about 50% and from Pisum of about 60%. 2.0 M NaCl or KCl reduced the enzyme activity of both Salicornia and Pisum to nearly 10% of control activity. Furthermore, in contrast to DCPIP reduction no stimulating effect of sulfates on glycolate oxidase activity was detectable. Indeed, the inhibitory effect of sulfates was very slight. 1.0 M Na2SO4 caused a mean inhibition of glycolate oxidase activity of only 15% with both species, and in the presence of 1.5 M Na2SO4 50% of control activity was measured. At maximal K2SO4 concentrations (0.5 M) glycolate oxidase from both Salicornia and Pisum was also unaffected. It is supposed that the described salt tolerance of glycolate oxidase in vitro, possibly is due to an adaptation of the enzyme to high salt levels within peroxisomes in vivo.  相似文献   

9.
The effects of NaCl on the internal and external carbonic anhydrase (CA) activity of several marine microalgae were studied. Unlike freshwater microalgae in which CA activity is generally inhibited by NaCl, marine microalgae exhibited considerable species-dependent variation when exposed to NaCl. CA activity in Phaeodactylum tricornutum, a diatom, was inhibited, whereas it was activated in the coccolithophorid Pleurochrysis carterae. CA activity in the chlorophyte Dunaliella primolecta was not significantly affected by NaCl. In Dunaliella salina and Dunaliella parva, NaCl inhibited external CA without affecting the internal activity, whereas in Chlorella vulgaris C-133 and Dunaliella peircei only the internal CA was inhibited. Internal CA of Dunaliella tertiolecta was not affected by NaCl, but the external enzyme was significantly enhanced. Salt substitution experiments revealed that chloride (Cl-) is the ion affecting CA activity; the effect of Cl- can be replaced by bromide ion. Cl- affects external CA activity while also affecting the apparent affinity for inorganic carbon during photosynthesis. Microalgae whose internal CA activity was enhanced by Cl- showed higher intracellular Cl- concentrations than those species that were inhibited.  相似文献   

10.
Increase in urease activity in leaves of Canavdlia ensifomis has been demonstrated. The activity of excised leaves increased by about 100 percent when 1.5 × 10?1M urea was added externally as inducer. Glycine-1-14C was used to investigate whether the increase in activity was dependent on de novo protein synthesis. The Incorporation of labeled amino acid into urease was twofold higher in induced samples than in non-induced ones. This indicates that the increase in activity is connected with de nova protein synthesis. The once increased activity was always followed by a rapid decrease. The urease activity was lost constantly with time after the external addition of ammonia in vivo. The inhibitory action of ammonia on urease fa vitro was eliminated by dialysis. Accordingly it may be concluded that the loss of activity was dependent on the product repression by ammonia.  相似文献   

11.
In succession to previous papers, screening experiments for ?-lysine acylase activity in microorganisms from soils have been carried out. As a result, the enzyme activity was observed in some soil bacteria. From the organisims showing the activity, the strain which showed the highest activity was isolated and the microorganism was confirmed to belong in Achromobacter pestifer. So, further screening experiments of the typical organisms of Achromobacter and Pseudomonas species have been carried out, but the found activity in several organisms was much lower than that in Achromobacter pestifer strain EA isolated by the authors. ?-Lysine acylase in this organism shows optical specificity and hydrolyses only L-isomer but not D-isomer of ?-acyllysine.  相似文献   

12.
ORTMEYER HK. Relationship of glycogen synthase and glycogen phosphorylase to protein phosphatase 2C and cAMP-dependent protein kinase in liver of obese rhesus monkeys. The regulation of glycogen synthase (GS) and glycogen phosphorylase (GP) activity by phosphorylation/ dephosphorylation has been proposed to be via changes in activities of several different protein (serine/ threonine) phosphatases and kinases, including protein phosphatase (PP) 1/2A, PP2C, and cAMP-dependent protein kinase (PKA). In order to determine whether PP1/2A, PP2C, and/or PKA activities are related to GS and/or GP activities, these enzymes were measured in freeze-clamped liver biopsies obtained under basal fasting conditions from 16 obese monkeys. Four monkeys were normoglycemic and normoinsulinemic, five were hyperinsulinemic, and seven had type 2 diabetes (NIDDM). Liver glycogen and glucose 6-phosphate (G6P) contents were also determined. Basal enzyme activities and basal substrate concentrations were not significantly different between the three groups of obese monkeys; however, there were several significant linear relationships observed when the monkeys were treated as one group. Therefore, multiple regression was used to determine the correlation between key variables. GS fractional activity was correlated to GP fractional activity (p<0. 05) and to PP2C activity (p=0. 005) (adjusted R2,53%). GP independent activity was correlated to GS independent activity (p<0. 07) and to PKA fractional activity (p=0. 005) (adjusted R2,64%). PP2C activity was correlated to GS fractional activity (p<0. 0005) and to PP1/2A activity G7<0. 0001) (adjusted R2,83%). PKA fractional activity was correlated to GP total activity (p<0. 0005) and to age (p=0. 001) (adjusted R282%). G6P content was correlated to glycogen content (p<0. 05) and to PP2C activity (p=0. 0005) (adjusted R2,73%). In conclusion, PP2C and PKA are involved in the regulation of GS and GP activity in the basal state in liver of obese monkeys with a wide range of glucose tolerance.  相似文献   

13.
14.
Phytase activity in rabbit cecal bacteria   总被引:1,自引:0,他引:1  
The presence of phytase activity was demonstrated in 26 strains of rabbit cecal bacteria. In 25 strains a low phytase activity, 0.10–0.62 μmol phosphate released per min per mg protein, was found. High activity (2.61 μmol/min per mg protein) was found in the strain PP2 identified as Enterococcus hirae. Phytase activity was cell-associated, being higher in the cell extract than in the cell walls. Extracellular phytase activity and cell-associated phosphatase activity were not detected. Phytase activity was optimal around pH 5.0, which is below the physiological cecal pH range. The K m determined using the Lineweaver-Burk plot was 0.19 μmol/mL. Cations Fe3+, Cu2+ and Zn2+ at 0.5 mmol/L decreased phytase activity in sonicated cells of E. hirae by 99.4, 90.7 and 96.5 %, respectively. In contrast, Mg2+ increased activity by 11.0 %. Characteristics of E. hirae phytase (pH optimum, K m, cation sensitivity) were similar to those of other bacterial phytases reported in the literature. Other bacteria with a high phytase activity may be present in the rabbit cecum but remain to be identified.  相似文献   

15.
The study was undertaken to evaluate changes in the activity of adenosine deaminase (ADA) in brains of rats infected by Trypanosoma evansi. Each rat was intraperitoneally infected with 106 trypomastigotes either suspended in fresh (group A; n = 13) and cryopreserved blood (group B; n = 13). Thirteen animals were used as control (group C). ADA activity was estimated in the cerebellum, cerebral cortex, striatum and hippocampus. No differences (P > 0.05) in ADA activity were observed in the cerebellum between infected and non-infected animals. Significant (P < 0.05) reductions in ADA activity occurred in cerebral cortex in acutely (day 4 post-infection; PI) and chronically (day 20 PI) infected rats. ADA activity was significantly (P < 0.05) decreased in the hippocampus in acutely infected rats, but significantly (P < 0.05) increased in the chronically infected rats. Significant (P < 0.05) reductions in ADA activity occurred in the striatum of chronically infected rats. Parasites could be found in peripheral blood and brain tissue through microscopic examination and PCR assay, respectively, in acutely and chronically infected rats. The reduction of ADA activity in the brain was associated with high levels of parasitemia and anemia in acute infections. Alterations in ADA activity of the brain in T. evansi-infected rats may have implications for pathogenesis of the disease.  相似文献   

16.
Abstract

Objectives

Some studies have indicated the pathophysiological importance of reactive oxygen species (ROS) in patients with nephrotic syndrome. Myeloperoxidase (MPO) is a leukocyte-derived enzyme-generating ROS that has been proposed to exert a wide array of pro-atherogenic effects throughout all stages of the atherosclerotic process. The aim of this study was to investigate the serum malondialdehyde (MDA) levels, MPO and catalase activities in patients with adult nephrotic syndrome.

Patients and Methods

Twenty-four patients with nephrotic syndrome and 24 healthy controls were enrolled. Serum MPO activity, catalase activity, and MDA levels were assessed.

Results

Serum MPO activity and MDA levels were signi?cantly higher in patients with nephrotic syndrome than controls (both, P < 0.001), while catalase activity was signi?cantly lower (P < 0.001). Serum catalase activity was found to be significantly correlated with MPO activity (r = ?0.417, P = 0.003) and MDA levels (r = ?0.532, P = 0.007). The serum MDA levels were also found to be significantly correlated with MPO activity (r = 0.419, P = 0.003).

Conclusions

We concluded that serum MPO activity and oxidative stress were increased and that serum catalase activity was decreased in patients with adult nephrotic syndrome. In addition, these results indicate that increased MPO activity is associated with an oxidant–antioxidant imbalance that may contribute to atherosclerosis in patients with adult nephrotic syndrome.  相似文献   

17.
Objective: The principal aim of this study was to validate a proposed new index of physical activity, the activity‐related time equivalent based on accelerometry (ArteACC), in adolescents. A secondary aim was to develop regression equations for prediction of total energy expenditure (TEE) and activity energy expenditure [AEE = 0.9 × TEE ? resting metabolic rate (RMR)]. Research Methods and Procedures: RMR and energy expenditure (EE) under standardized exercises were measured by indirect calorimetry in 36 adolescents (14 to 19 years old). TEE was measured by the doubly labeled water method, and physical activity was assessed simultaneously with an accelerometer for 14 days. AEE, AEE in relation to body weight (AEE per kilogram), and activity‐related time equivalent based on energy expenditure (ArteEE = AEE/[EE reference activity ? RMR]) were calculated from laboratory and free‐living EE data. ArteACC was calculated as total activity counts/activity counts of reference activity. Results: ArteACC was significantly related to AEE per kilogram (r = 0.57; p < 0.0001) and ArteEE (r = 0.68; p < 0.001). The absolute amount of time (minutes per day) spent in physical activity was significantly lower when calculated from ArteACC than from ArteEE (p < 0.001). TEE was significantly influenced by RMR, sex, and ArteACC (r2 = 0.89). AEE was significantly influenced by sex and ArteACC (r2 = 0.59). Discussion: Despite an absolute difference between the two indexes, ArteEE and ArteACC, ArteACC seems to be a valid indicator of free‐living physical activity. It contributed significantly, by 3.3% and 12.5%, to the explained variations in TEE and AEE, respectively.  相似文献   

18.
The subcellular distribution of four enzymes (glucose-6-phosphatase, phosphodiesterase I, NADPH-cytochrome c reductase, and p-nitroanisole O-demethylase) in the midgut of “wandering” fifth-instar larvae of the tobacco hornworm, Manduca sexta (L), was determined and the composition of mitochondrial and microsomal pellets was examined by electron microscopy. Most of the glucose-6-phosphatase activity and one-third of the phosphodiesterase I activity were found in the high-speed supernatant. NADPH-cytochrome c reductase activity was marginal and O-demethylase activity was undetectable in the supernatant. The highest specific activities for phosphodiesterase I, NADPH-cytochrome c reductase, and p-nitroanisole O-demethylase were measured in microsomes, but the relative specific activity of phosphodiesterase I was only half that obtained with the latter two enzymes. In all subcellular preparations the relative specific activities of NADPH-cytochrome c reductase and p-nitroanisole O-demethylase were closely correlated. It is concluded that glucose-6-phosphatase and phosphodiesterase I are not microsomal marker enzymes in the midgut, but the activities of NADPH-cytochrome c reductase and p-nitroanisole O-demethylase are quantitative measures of microsomal content.  相似文献   

19.
The appearance of NO2 ? reducing activity of cytochrome c (Cyt c) upon heat denaturation was investigated with equine heart Cyt c. Denatured equine heart Cyt c (dCyt c), which was treated at 100°C for 30 min, had NO2 ? reducing activity in the presence of dithionite and methylviologen in an aqueous solution under anaerobic conditions. In contrast, hemoglobin and myoglobin had no such activity under the same conditions. Using spectroscopic methods, we found that the appearance of this activity in the Cyt c was due to the following intramolecular changes: unfolding of the peptide chain, exposure of the heme, dissociation of the sixth ligand methionine sulfur, and appearance of autoxidizability. The dCyt c catalyzed NO2 ? reduction to NH4 + via ferrous-NO complexes, and this reaction was a 6-electron and 8-proton reduction. Sepharose-immobilized dCyt c had activity similar strength to that in solution. The resin retained the activity after five uses and even after storage for 1 year. On the basis of these results, we concluded that Cyt c acquired a new catalytic activity upon heat treatment, unlike to other familiar biological molecules.  相似文献   

20.
Objective: This study aimed to describe levels of physical activity in a representative sample of preschool children and to quantify tracking of activity over 1 year. Research Methods and Procedures: Physical activity (mean accelerometry counts/minute) was assessed over 3 days using the Computer Science and Applications accelerometer in 3‐ to 4‐year‐old children (n = 104; 52 boys; mean age, 3.7 ± 0.4 years). In 60 children (30 boys), measurements were repeated 1 year later. Results: Mean total activity at baseline was 777 ± 207 counts/minute in boys and 657 ± 172 counts/minute for girls; this gender difference was significant (p < 0.001). In the cross‐sectional analysis, total activity was significantly positively related to age (r = 0.37, p = 0.007). In the sample followed up for 1 year, mean total activity was 849 ± 252. The longitudinal analysis confirmed that total physical activity increased over the 1‐year period (paired Student's t test, p < 0.001). The tracking rank order correlation coefficient of total activity count over 1 year was r = 0.40 (p < 0.001). Discussion: This study suggests that total activity increases during the preschool period in Scottish children and that gender differences in total activity are present early in life. Tracking of total activity was only modest, but adequate assessment of tracking requires methodological research aimed at elucidating the biological meaning of accelerometer output.  相似文献   

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