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1.
The main objective of this work was studying and testing the nature and influence of reaction media (organic solvent vs. miniemulsion system) on the synthesis of alkyl esters catalyzed by Fusarium solani pisi cutinase. Ester synthesis and cutinase selectivity for different chain length of acids and alcohols (ethyl and hexyl) were evaluated. In iso-octane, after 1 h of reaction, cutinase exhibits rates of esterification between 0.24 μmol x mg1 x min–1 for ethyl oleate and 1.15 μmol x mg1 x min–1 for ethyl butyrate, while in a miniemulsion system the rates were from 0.05 for ethyl heptanoate to 0.76 μmol x mg–1 x min–1 for ethyl decanoate. The reaction rate for the synthesis of hexyl esters in a miniemulsion system was from 0.19 for hexyl heptanoate to 1.07 μmol x mg1 x min–1 for hexyl decanoate. High conversion yields of 95% at equilibrium after 8 h of reaction in iso-octane for pentanoic acid (C5) with ethanol at equimolar concentration (0.1 M) was achieved. Additionally, this work showed that a significant and unexpected shift in cutinase selectivity occurred towards longer chain length carboxylic acids (C8–C10) in miniemulsion system as compared to organic solvent (iso-octane) and previous studies in reverse micellar systems. The possibility of working with higher concentration of substrates, without inhibitory effect on the enzyme, was another advantage of the miniemulsion system.  相似文献   

2.
Submitochondrial particles (SMP) were produced from Jerusalem artichoke (Helianthus tuberosus L.) mitochondria by sonication and differential centrifugation. The SMP were about 50% inside-out as measured by the access of reduced cytochrome c to cytochrome c oxidase. Uncoupled NADH oxidation (1 mM NADH) by the SMP was 120 nmol O2 min?1mg?1, which was reduced to 98 nmol O2 min?1 (mg mitochondrial protein)?1 in the presence of EGTA. In contrast, the oxidation of NADH by intact mitochondria was completely inhibited by EGTA (from 182 to 14 nmol O2 min?1mg?1). The EGTA-resistant NADH oxidation by the SMP is ascribed to the NADH dehydrogenase(s) on the inside of the inner membrane and exposed to the medium in the inside-out SMP. In the presence of EGTA it could be shown that two NADH dehydrogenase activities were present in the SMP. One had an apparent Km of 7 μM for NADH, a Vmax of 80 nmol NADH min?1mg?1, and was rotenone-sensitive. This dehydrogenase is equivalent to the mammalian Complex I NADH dehydrogenase. The other dehydrogenase, which was rotenone-resistant, had a Km of 80 μM and a Vmax of 131 nmol NADH min?1mg?1; it is probably responsible for the rotenone-resistant oxidation of organic acids often observed in plant mitochondria. The redox poise of the pyridine nucleotides had only a small effect on the relative rates of the two internal dehydrogenases. Electron flow through these dehydrogenases appears, therefore, to be regulated mainly by the concentration of NADH in the matrix of the mitochondria.  相似文献   

3.
A quantitative radiometric high-pressure liquid chromatography assay for the estimation of the three main oxidative metabolites of antipyrine in vitro using [3-14C]antipyrine as substrate is described. Baseline separation of antipyrine, 3-hydroxymethylantipyrine, 4-hydroxyantipyrine, and norphenazone was achieved, after methylation, using a reverse-phase μBondapak C18 column with a mobile phase of 17% acetonitrile in water. The metabolites could be estimated free of interference as confirmed by gas chromatography-mass spectrometry. Unlabeled metabolites were used as recovery standards. Activity could be determined with as little as 100 μg human liver microsomal protein. Maximum velocities for the formation of the three metabolites ranged from 1 to 3.5 nmol product mg?1 min?1 with rat liver and from 0.3 to 0.6 nmol product mg?1 min?1 with human liver.  相似文献   

4.
The effect of irradiance and temperature on the photosynthesis of the red alga, Pyropia tenera, was determined for maricultured gametophytes and sporophytes collected from a region that is known as one of the southern limits of its distribution in Japan. Macroscopic gametophytes were examined using both pulse‐amplitude modulated fluorometry and/or dissolved oxygen sensors. A model of the net photosynthesis–irradiance (P‐E) relationship of the gametophytes at 12°C revealed that the net photosynthetic rate quickly increased at irradiances below the estimated saturation irradiance of 46 μmol photons m?2 s?1, and the compensation irradiance was 9 μmol photons m?2 s?1. Gross photosynthesis and dark respiration for the gametophytes were also determined over a range of temperatures (8–34°C), revealing that the gross photosynthetic rates of 46.3 μmol O2 mgchl‐a?1 min?1 was highest at 9.3 (95% Bayesian credible interval (BCI): 2.3–14.5)°C, and the dark respiration rate increased at a rate of 0.93 μmol O2 mgchl‐a?1 min?1°C?1. The measured dark respiration rates ranged from ?0.06 μmol O2 mgchl‐a?1 min?1 at 6°C to ?25.2 μmol O2 mgchl‐a?1 min?1 at 34°C. The highest value of the maximum quantum yield (Fv/Fm) for the gametophytes occurred at 22.4 (BCI: 21.5–23.3) °C and was 0.48 (BCI: 0.475–0.486), although those of the sporophyte occurred at 12.9 (BCI: 7.4–15.1) °C and was 0.52 (BCI: 0.506–0.544). This species may be considered well‐adapted to the current range of seawater temperatures in this region. However, since the gametophytes have such a low temperature requirement, they are most likely close to their tolerable temperatures in the natural environment.  相似文献   

5.
N-Nitrosodimethylamine (NDMA) is an emerging contaminant of concern. N-nitrodimethylamine (DMNA) is a structural analog to NDMA. NDMA and DMNA have been found in drinking water, groundwater, and other media and are of concern due their toxicity. The authors evaluated biotransformation of NDMA and DMNA by cultures enriched from contaminated groundwater growing on benzene, butane, methane, propane, or toluene. Maximum specific growth rates of enriched cultures on butane (μmax = 1.1 h?1) and propane (μmax = 0.65 h?1) were 1 to 2 orders of magnitude higher than those presented in the literature. Growth rates of mixed cultures grown on benzene (μmax = 1.3 h?1), methane (μmax = 0.09 h?1), and toluene (μmax = 0.99 h?1) in these studies were similar to those presented in the literature. NDMA biotransformation rates for methane oxidizers (υmax = 1.4 ng min?1 mg?1) and toluene oxidizers (υmax = 2.3 ng min?1 mg?1) were comparable to those presented in the literature, whereas the biotransformation rate for propane oxidizers (υmax = 0.37 ng min?1 mg?1) was lower. NDMA biotransformation rates for benzene oxidizers (υmax = 1.02 ng min?1 mg?1) and butane oxidizers (υmax = 1.2 ng min?1 mg?1) were comparable to those reported for other primary substrates. These studies showed that DMNA biotransformation rates for benzene (υmax = 0.79 ng min?1 mg?1), butane (υmax = 1.0 ng min?1 mg?1), methane (υmax = 2.1 ng min?1 mg?1), propane (υmax = 1.46 ng min?1 mg?1), and toluene (υmax = 0.52 ng min?1 mg?1) oxidizers were all comparable. These studies highlight potential bioremediation methods for NDMA and DMNA in contaminated groundwater.  相似文献   

6.
Two different immobilisation techniques for lipases were investigated: adsorption on to Accurel EP-100 and deposition on to Celite. The specific activities were in the same order of magnitude, 2.9 (mol min–1 mg protein) when Celite was used as support and 2.3 (mol min–1 mg–1 protein) when Accurel EP-100 was used as support, even if the amount of lipase loaded differed by 2 orders of magnitude. Immobilisation on Accurel EP-100 was the preferred technique since 40–100 times more protein can be loaded/per g carrier, thus yielding a more active catalyst. The water activity profiles in lipase catalysed esterification were influenced by the amount of protein adsorbed to Accurel EP-100. Higher protein loading (40 mg g–1) resulted in a bell-shaped water activity profile with highest specific activity (6.1 mol min–1 mg–1 protein) at a w=0.11, while an enzyme preparation with low protein loading (4 mg g–1) showed highest specific activity at a w=0.75.  相似文献   

7.
The inhibition of neuraminidase from Clostridium chauvoei (jakari strain) with partially purified methanolic extracts of some plants used in Ethnopharmacological practice was evaluated. Extracts of two medicinal plants, Tamarindus indicus and Combretum fragrans at 100–1000 μg/ml, both significantly reduced the activity of the enzyme in a dose-dependent fashion (P < 0.001).

The estimated IC50 values for Tamarindus indicus and Combretum fragrans were 100 and 150 μ/ml respectively. Initial velocity studies conducted, using fetuin as substrate revealed a non-competitive inhibition with the Vmax significantly altered from 500 μmole min?1 mg?1 to 240μmole min?1 mg?1 and 340 μmole min?1 mg?1 in the presence of Tamarindus indicus and Combretum fragrans respectively. The KM remained unchanged at 0.42 mM. The computed Index of physiological efficiency was reduced from 1.19 min?1 to 0.57 min?1 and 0.75 min?1 with Tamarindus indicus and Combretum fragrans as inhibitors respectively.  相似文献   

8.
《Biomarkers》2013,18(4):267-272
Abstract

Sulphonamide hypersensitivity reactions are believed to be mediated through reactive intermediates derived from oxidation of the paraamino group to form sulphonamide hydroxylamines. Sulphamethoxazole hydroxylamine (SMX-HA) can be acetylated by N-acetyltransferase (NAT) enzymes to form an acetoxy metabolite (acetoxySMX). In the current studies, acetoxySMX was found to be not toxic over the concentration range of 0 to 500 μM towards a human lymphoblastoid cell line (RPMI 1788) or a human hepatoma cell line (HepG2). Further, transient expression of NAT1 in COS-1 cells or stable transfection of NAT1 andNAT2 in HepG2 cells did not alter the toxicity of SMX-HA in vitro. The activity of NAT1 in isolated mononuclear leucocytes (a reflection of systemic NAT1 activity) determined with paraaminobenzoic acid as a substrate was not different between controls (n = 11) or patients with a known hypersensitivity reaction (n = 5) (4.1 ±1.2 nmol min?1mg?1 vs 5.7 ± 1.4 nmol min?1 mg?1). Thus, acetoxy SMX is unlikely to play a significant role in mediating SMX hypersensitivity reactions anda constitutive deficiency in NAT1 activity is not a common finding in patients susceptible to SMX hypersensitivity reactions.  相似文献   

9.
Versicolorin A hemiacetal was converted to versicolorin C in cell-free systems fromAspergillus parasiticus. The rate of reaction catalyzed by the 35–70% ammonium sulfate fraction was 0.43 nmol min–1 mg–1 with NADPH as cosubstrate and 0.17 nmol. min–1 mg–1 with NADH at 25°C at pH 7.4. The product from incubation of 17-hdyroxy-16,17-dihydrosterigmatocystin with the 35–70% ammonium sulfate fraction and NADPH was a polar compound which was converted to dihydrosterigmatocystin by 0.4 M HCl. The olar comound is proposed to be the 14,17-hydrated open-chain derivative of dihydrosterigmatocystin. Aflatoxin G2a was also reduced in this system to a polar product tentatively identified as the 13,16-hydrated open-chain derivative of AFG2. The reductase activity may be involved in the formation of reduced intermediates and aflatoxins in cultures ofA. parasiticus.  相似文献   

10.
We analyzed the effect of lysophosphatidylcholine (lysoPC) on the activity of the plasma membrane (PM) H+-AT-Pase measured at pH 6.3 or 7.5 in inside-out PM vesicles isolated from germinating radish seeds. LysoPC stimulated PM H+-ATPase at both pHs, but the dependence of the effect on lysoPC concentration was different: at pH 6.3 maximal stimulation was observed with 40 to 200 μg ml?1 lysoPC, while at pH 7.5 a sharp peak of activation was observed at about 50 μg ml?1 lysoPC, higher concentrations becoming dramatically inhibitory; this inhibitory effect was considerably reduced in the presence of 10% (v/v) glycerol. In trypsin-treared PM lysoPC stimulated the H+-ATPase activity assayed at pH 6.3, but only marginally that assayed at pH 7.5. LysoPC increased both Vmax (from 190 to 280nmol min?1 mg?1 prot) and apparent KM (from 0.15 to 0.3 mM) of the H+-ATPase at pH 6.3, while it increased Vmax (from 120 to 230 nmol min?1 mg?1 prot) and decreased apparent Km (from 0.8 to 0.4 mM) at pH 7.5. Low concentrations of Nacetylimidazole (10 to 50 mM), which modifies tyrosine residues, abolished the stimulation by lysoPC of the PM H+-ATPase activity at pH 7.5, but not that observed at pH 6.3. These results indicate that lysoPC influences the PM H+-ATPase through different mechanisms, and that its effect can only partly be ascribed to its ability to hamper the inhibitory interaction of the regulatory C-terminal domain with the catalytic site. N-acety-limidazole did not affect the stimulation of PM H+-ATPase by controlled trypsin treatment or by fusicoccin, indicating that the requirement for the tyrosine residue(s) modified by low Nacetylimidazole concentrations is specific for lysoPC-induced displacement of the C-terminal domain.  相似文献   

11.
Abstract

Present study was undertaken to develop cross-linked enzyme aggregate (CLEA)of alkaline serine proteases (sp) from Pythium myriotylum (Pm), a necrotrophic oomycete reported to considerably secrete serine proteases. Among various precipitants screened for spPm1-CLEA preparation, ammonium sulfate at 80% saturation (w/v) yielded 100% activity recovery and retention of spherical morphology as observed by SEM analysis. Addition of glutaraldehyde as cross-linker at 1% (v/v) concentration with optimized ammonium sulfate concentration for 1?hour at 100?rpm yielded 100% activity recovery of spPm1-CLEA from 8-day old P. myriotylum culture filtrate. Addition of BSA (10?mg/ml) to CLEA cross-linking reaction mix reduced CLEA size from the range of 1.82–1.19?µm to 394–647?nm. spPm1-CLEA preparations retained 100% activity at temperature of 80?°C and pH 12.0 signifying their potential commercial applications. In terms of kinetic parameters, present process enhanced kinetic parameters as revealed by 1.67?U.mg?1 specific activity, Km of 0.062?mM and Vmax of 0.145?µmol.min?1.mg?1 for the spPm1-CLEA compared to 0.288?U.mg?1 specific activity, Km of 0.060?mM and Vmax of 0.20?µmol.min?1.mg?1 determined for the free spPm1 enzyme. Study has successfully demonstrated the concept of CLEA in enhancing spPm1 stability and the results so generated can be translated in future towards development of robust biocatalysts.  相似文献   

12.
Neuronal nitric oxide synthase (nNOS) was purified on DEAE-Sepharose anion-exchange in a 38% yield, with 3-fold recovery and specific activity of 5 µmol.min?1.mg?1. The enzyme was a heterogeneous dimer of molecular mass 225?kDa having a temperature and pH optima of 40°C and 6.5, Km and Vmax of 2.6 μM and 996 nmol.min?1.ml?1, respectively and was relatively stable at the optimum conditions (t½?=?3?h). β-Amyloid peptide fragments Aβ17–28 was the better inhibitor for nNOS (Ki?=?0.81 µM). After extended incubation of nNOS (96?h) with each of the peptide fragments, Congo Red, turbidity and thioflavin-T assays detected the presence of soluble and insoluble fibrils that had formed at a rate of 5?nM.min?1. A hydrophobic fragment Aβ17–21 [Leu17 – Val18 – Phe19 – Phe20 – Ala21] and glycine zipper motifs within the peptide fragment Aβ17–35 were critical in binding and in fibrillogenesis confirming that nNOS was amyloidogenic catalyst.  相似文献   

13.
Parameters of degradation of p-toluenesulfonate (TS) by free and agar-embedded Comamonas testosteroni BS1310 (pBS1010) cells were determined. The maximum rate of TS degradation was 25% lower in immobilized than free cells, equaling 11 nmol min?1 mg?1 cells. Degradation of TS by both free and immobilized cells was associated with molecular oxygen consumption (molar ratio 1 : 2). In a plug-flow reactor, the degradation rate was 10.4 nmol min?1 mg?1 cells. The results can be applied to designing reactors for TS degradation in sewage and developing biosensors.  相似文献   

14.
Δ53β hydroxysteroid dehydrogenase activity transforms biologically inactive Δ53β hydroxy steroids into the active Δ43-keto products (e.g. pregnenolone to progesterone). Using a cytochemical procedure which allows for the continuous microdensitometric monitoring of an enzyme reaction as it proceeds and a well described cytochemical assay for Δ53β HSD we have analysed the initial velocity rates (Vo) for dehydroepiandrosterone (DHEA) binding to this enzyme in regressing (i.e. 20α hydroxy steroid dehydrogenase positive) corpus luteum (CL) cells in unfixed tissue sections (5 μm) of the dioestrous and proestrous rat ovary. The results are mean ± S.E.M. The relationship between DHEA concentration (0 to 50 μM) and Δ53β HSD activity in the dioestrous corpora lutea was sigmoidal and had an atypical 1/Vo versus 1/S plot, the x intercept being positive. Using a 1/Vo versus 1/S2 plot the Vmax was determined to be 1·0 ± 0·08 μmol min?1 mg?1 CL (n = 6). The Hill constant was 2·7 ± 0·02 (n = 6) suggesting a high degree of positive co-operativity for DHEA binding. The S concentration for half maximal activity was 17 ± 1 μmoles (n = 6). In the corpora lutea cells of the proestrous ovary, the Vmax for DHEA transformation was unchanged (0·95 ± 0·04 μmol min?1 mg?1, n = 3) whilst the S0·5 was significantly increased to 27 ± 0·1 (p < 0·01, n = 3). The Hill constant remained positive being 2·9 ± 0·2 (n = 3). NAD+ binding to 3β HSD in regressing corpora lutea of the proestrous ovary has been demonstrated previously to be hyperbolic and fit the classical Michaelis-Menten model.1 Extending the analysis of NAD+ binding to the regressing corpus luteum of the dioestrous rat ovary revealed similar kinetic characteristics to that seen with the proestrous enzyme, the apparent Vmax and Km being 0·84 ± 0·04 μmol min?1 mg?1 CL (n = 3) and 27 ± 7 μmol 1?1 (n = 3) respectively. The Hill constant was 1·1 ± 0·03 (n = 3), indicating no co-operativity of co-factor binding.  相似文献   

15.
Desulfotomaculum acetoxidans oxidizes acetate to CO2 with sulfate. This organism metabolizes acetate via a pathway in which C1 units rather than tri- and dicarboxylic acids are intermediates. We report here that cell extracts of D. acetoxidans catalyzed an exchange between CO2 and the carboxyl group of acetate at a rate of 90 nmol · min-1 · mg-1 protein which is sufficient to account for the in vivo acetate oxidation rate of 250 nmol · min-1 · mg-1 protein. The reaction was strictly dependent on both ATP and coenzyme A. The extracts contain high activities of acetate kinase (6.3 U · mg-1 protein) and phosphotransacetylase (60 U · mg-1 protein). These findings indicate that acetyl-CoA rather than acetyl-phosphate or acetate is the substrate of the carbon-carbon cleavage activity. Exchange was only observed in the presence of strong reducing agents such as Ti3+. Interestingly, the cell extracts also catalyzed the reduction of CO2 to CO with Ti3+ as electron donor (120 nmol · min-1 · mg-1 protein). Carbon monoxide dehydrogenase and other oxidoreductases involved in acetate oxidation were found to be partially associated with the membrane fraction suggesting a membrane localization of these enzymes.Abbreviations MOPS Morpholinopropane sulfonic acid - Tricine N-tris(hydroxymethyl)-methylglycine - DTT d,l-1,4-Dithiothreitol - DMN 2,3-Dimethyl-1,4-naphthoquinone - MVOX Methyl viologen, oxidized - APS Adenosinephosphosulfate - SRB Sulfate reducing bacteria - U mol product formed per min  相似文献   

16.
Choline kinase (EC 2.7.1.32; ATP: choline phosphotransferase) was purified 200-fold from an extract of acetone powder of rabbit brain by a combination of acid precipitation, ammonium sulphate precipitation, DEAE cellulose chromatography, and ultrafiltration. Maximal activity of 243 nmol of phosphorylcholine synthesized. min?1 mg?l of protein occurred at pH 9.5–10.0 in the presence of 10 mm MgS04, 10 mm choline and 0.005% (w/v) bovine serum albumin. 2-Aminoethanol, 2-methylaminoethanol, and 2-dimethylaminoethanol were also phosphorlyated by the enzyme preparation. The enzyme quantitatively converted low concentrations of choline (2.5–50 μm ) to phosphorylcholine [32P] in the presence of ATP [y32P], and may, therefore, be used to measure small amounts of choline acetylcholine. There were two Km values for choline at pH 9.5; 32 μm and 0.31 mm . At pH 7.4, the higher Km was not observed and enzyme activity was maximal with 0.1 mm choline. The Km for ATP was 1.1 mm . Enzyme activity was inhibited by ATP (20 mm ), AMP, ADP, cytidine diphosphocholine (1 or 10 mm ), and activated by choline esters (1.0 mm ), NaCl or KCl(200 mm ).  相似文献   

17.
Stomatal responses to leaf temperature (Tl) and to the mole fractions of water vapour in the ambient air (wa) and the leaf intercellular air spaces (wi) were determined in darkness to remove the potential effects of changes in photosynthesis and intercellular CO2 concentration. Both the steady‐state and kinetic responses of stomatal conductance (gs) to wa in darkness were found to be indistinguishable from those in the light. gs showed a steep response to the difference (Δw) between wa and wi when wa was varied. The response was much less steep when wi was varied. Although stomatal apertures responded steeply to Tl when Δw was held constant at 17 mmol mol?1, the response was much less steep when Δw was held constant at about zero. Similar results were obtained in the light for Δw = 15 mmol mol?1 and Δw ≈ 0 mmol mol?1. These results are discussed in the context of mechanisms for the stomatal response to humidity.  相似文献   

18.
The synthesis of glutamate from 2-oxoglutarate generated by the citric acid cycle and ammonium acetate has been studied in brain mitochondria of synaptic or non synaptic origin. Non synaptic brain mitochondria synthesise glutamate at twice the rate (1.3 nmol. min?1. mg protein?1) of synaptic mitochondria (0.65 nmol. min?1. mg protein?1) when pyruvate is the precursor for 2-oxoglutarate, but at a similar rate (0.9 and 0.7 nmol. min?1, mg protein?1) when 3 hydroxybutyrate is the precursor. Glutamate synthesis from ammonium acetate and extramitochondrially addcd 2-oxoglutarate (5 mM) by both synaptic and nonsynaptic mitochondria was 5-fold higher (5-6nmol. min?1. mg protein?1) than glutamate synthesis from endogenously produced 2-oxoglutarate. In the uncoupled state (or un-coupler + oligomycin) the rate was reduced by half. (2.5-3 nmol. min?1. mg protein?1) as compared to mitochondria synthesising glutamate in states 3 or 4 (± oligomycin). The changes in brain mitochondrial nicotinamide nucleotide redox state have been monitored by fluorimetric, spectrophotometric and enzymatic techniques during glutamate synthesis and compared with liver mitochondria under similar conditions. On the instigation of glutamate synthesis by NH+4 addition a significant NAD(P)H oxidation occurs with liver mitochondria but no detectable change occurs with brain mitochondria. Leucine (2 mM) causes a doubling of glutamate synthesis by both synaptic and non synaptic brain mitochondria with no detectable change in the NAD(P)H redox state. The results are discussed with respect to the control of glutamate synthesis by mitochondrial redox potential and the possible intramitochondrial compartmentation of this process.  相似文献   

19.
For a purified preparation of the soluble form of phosphatidate phosphohydrolase (EC 3.1.3.4) from guinea pig cerebral cortex, 1-O-alkyl-rac-glycerol 3-phosphate was found to be accepted as a substrate. This substrate analog was tritium-labeled in order to serve in a rapid sensitive assay for the enzyme, in which labeled 1-alkyl glycerol is released. Heat denaturation and enzyme activity dependence on pH indicated that 1-O-alkyl-rac-glycerol 3-phosphate phosphohydrolase and phosphatidate phosphohydrolase activities in the preparation are attributable to the same enzyme. 1-O-Alkyl-rac-glycerol 3-phosphate was hydrolyzed with a Vmax of 1.7 nmol min?1 mg?1 of protein and a Km of 270 μm.  相似文献   

20.
The effects of ethylene (C2H4) on tetrasporogenesis of the red seaweed Pterocladiella capillacea (S. G. Gmelin) Bornet were investigated. Ethylene is a gaseous hormone that is involved in a variety of physiological processes (e.g., flowering, fruit abscission) in higher plants. To study the effects of ethylene on the reproduction of the red seaweed P. capillacea, immature tetrasporophytic thalli were exposed to a flow of ethylene for different time periods. Maximum maturation of tetrasporangia was observed at 7 d in thalli exposed to ethylene for 15 min. This maturation was accompanied by a significant increase in the free fraction of putrescine (Put) and a 5‐fold increase in the level of total RNA. These changes were specifically due to ethylene since they were blocked by the presence of the ethylene perception inhibitor silver thiosulphate (STS). Moreover, P. capillacea was determined to produce ethylene at a rate of 1.12 ± 0.06 nmol ethylene · h?1· g?1 fresh weight (fwt) with specific activities for 1‐aminocyclopropane‐1‐acrylic acid (ACC) synthase of 11.21 ± 1.19 nmol ethylene · h?1· mg?1 protein and for ACC oxidase (ACO) of 7.12 ± 0.11 nmol ethylene · h?1· mg?1 protein. We conclude that ethylene may indeed be a physiological regulator of tetrasporogenesis in this red seaweed.  相似文献   

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