Soil pH and phosphatase activity

Abstract

Approximately twenty years before this study, a site that consisted of a mixed oak forest was harvested, cleared, and divided into three treatment areas consisting of approximately 20 acres each. The three areas were planted to oak (forest), grass (grassland) and corn (agricultural) respectively. The influence of pH on the rate of phosphatase activity was determined over a broad range of soil pH in soil sampled from each treatment area. Phosphomonoesterase activities were measured at a pH of 2 through 12 and phosphodiesterase activities determined at a pH of 4 through 12. In the forest soil only a acid phosphomonoesterase was detected whose pH optima was maximal at the measured soil pH of 4.9. A neutral phosphomonoesterase was found in the grassland soil, pH 6.6, with a broad pH optima ranging from 4.6 to 7.0, while the detection of an acid phosphatase and a alkaline phosphatase, with a pH optima of 4.8 and 11.0 respectively, was found associated with the agriculture soil with a measured pH of 7.2. Phosphodiesterase activity was optimum or near optimum at the measured pH of each soil examined. The released phosphatases apparently have different pH optima in relation to maximal activity suggesting the presence of different kinds of phosphomonoesterases and phosphodiesterases and perhaps that the enzymatic reaction in soil is catalyzed by more than one enzyme or by multiple forms of the same enzyme. The results of the study would indicate that a relationship exists between soil pH and (1) the synthesis and release of phosphatases in soil, (2) the complexion of the organisms producing the enzymes and (3) phosphatase stability or conformation. Based upon the results of the study, the analysis of phosphatase activity at the measured soil pH would seem to be a necessary part of any investigation designed to determine the contribution of phosphatase enzymes to the cycling of P.     

Purification and characterization of a lipoxygenase enzyme from durum wheat semolina.

Purification of a lipoxygenase enzyme from the cultivar Tresor of durum wheat semolina (Triticum turgidum var. durum Desf) was reinvestigated furnishing a new procedure. The 895-fold purified homogeneous enzyme showed a monomeric structure with a molecular mass of 95 +/- 5 kDa. Among the substrates tested, linoleic acid showed the highest k(cat)/K(m) value; a beta-carotene bleaching activity was also detected. The enzyme optimal activity was at pH 6. 8 on linoleic acid as substrate and at pH 5.2 for the bleaching activity on beta-carotene, both assayed at 25 degrees C. The dependence of lipoxygenase activity on temperature showed a maximum at 40 degrees C for linoleic acid and at 60 degrees C for bleaching activity on beta-carotene. The amino acid composition showed the presence of only one tryptophan residue per monomer. Far-UV circular dichroism studies carried out at 25 degrees C in acidic, neutral, and basic regions revealed that the protein possesses a secondary structure content with a high percentage of alpha- and beta-structures. Near-UV circular dichroism, at 25 degrees C and at the same pH values, pointed out a strong perturbation of the tertiary structure in the acidic and basic regions compared to the neutral pH condition. Moreover, far-UV CD spectra studying the effects of the temperature on alpha-helix content revealed that the melting point of the alpha-helix is at 60 degrees C at pH 5.0, whereas it was at 50 degrees C at pH 6.8 and 9.0. The NH(2)-terminal sequence allowed a homology comparison with other lipoxygenase sequences from mammalian and vegetable sources.     

产纤维素酶菌群的筛选及其酶学特性研究

从常年堆放的腐质豆秆中分离到1组产纤维素酶菌群MO,并在50℃、pH8.0条件下培养,90h时达到最高酶活,活性为1.3611IU。该酶最适反应温度为60℃,pH为7.0,在60℃以下和pH3~8范围内具有良好的热稳定性和pH稳定性。在最适反应条件下,该酶的最高活性可达2.13IU。通过生长动力学研究了菌群内部不同生长阶段pH、酶活和失重率的相互关系,并通过非变性电泳对酶谱进行初步研究,得到7条活性条带,说明MO中具有多种产酶菌株。     

Characterization and histochemical localization of nonspecific esterase from ascocarps of desert truffle (Terfezia claveryi Chatin)

An esterase activity from Terfezia claveryi Chatin ascocarps, a mycorrhizal hypogeous fungus, is described for the first time. The enzyme was partially purified using phase partitioning in Triton X-114 (TX-114), achieving a reduction of 87% in the triglyceride content and the removal of 63% of phenols. The enzyme showed maximum activity toward short-chain p-nitrophenyl esters, and no interfacial activation was observed, indicating that the enzyme responsible for this activity is an esterase and not a lipase. This esterase presented its maximum activity at pH 7.4 and 60 degrees C. The values obtained for Km at pH 7.4 were 0.3 mM for p-nitrophenyl butyrate and 0.6 mM for p-nitrophenyl acetate with catalytic efficiencies (Vmax/Km) of 0.23 and 0.32, respectively. T. claveryi esterase was inhibited by phenylboric acid, indicating that serine residues were involved in the enzyme activity. This activity was localized only in the hypothecium and was absent from the peridium and gleba.     

里氏木霉木聚糖酶基因Ⅱ在毕赤酵母中的分泌表达及其酶学性质研究

利用RT-PCR技术从高产木聚糖酶菌株T. reesei Rut C-30中成功扩增出其主要木聚糖酶基因XynⅡ,经序列分析证实,在该菌株诱变选育过程中其成熟肽序列有两处碱基发生突变;将不带原基因信号肽的XynⅡ克隆到毕赤酵母高效表达载体pPICZαA上,线性化后经电击转化到毕赤酵母中,经Zeocin及PCR筛选后得到的转化子用1%甲醇诱导。SDS-PAGE证实,重组子实现了分泌表达,且发酵上清中几无杂蛋白;对该重组酶酶学性质分析表明,该酶最适反应温度为60℃,最适反应pH值为6.0,该酶热稳定性较好,在50℃下保温30 min仍能保留其95%以上活性。     

Cloning, expression, and characterization of a D-psicose 3-epimerase from Clostridium cellulolyticum H10

The noncharacterized protein ACL75304 encoded by the gene Ccel_0941 from Clostridium cellulolyticum H10 (ATCC 35319), previously proposed as the xylose isomerase domain protein TIM barrel, was cloned and expressed in Escherichia coli . The expressed enzyme was purified by nickel-affinity chromatography with electrophoretic homogeneity and then characterized as d-psicose 3-epimerase. The enzyme was strictly metal-dependent and showed a maximal activity in the presence of Co(2+). The optimum pH and temperature for enzyme activity were 55 °C and pH 8.0. The half-lives for the enzyme at 60 °C were 6.8 h and 10 min when incubated with and without Co(2+), respectively, suggesting that this enzyme was extremely thermostable in the presence of Co(2+) but readily inactivated without metal ion. The Michaelis-Menten constant (K(m)), turnover number (k(cat)), and catalytic efficiency (k(cat)/K(m)) values of the enzyme for substrate d-psicose were estimated to be 17.4 mM, 3243.4 min(-1), and 186.4 mM min(-1), respectively. The enzyme carried out the epimerization of d-fructose to d-psicose with a conversion yield of 32% under optimal conditions, suggesting that the enzyme is a potential d-psicose producer.     

Effect of temperature and/or pressure on tomato pectinesterase activity

The activity of tomato pectinesterase (PE) was studied as a function of pressure (0.1-900 MPa) and temperature (20-75 degrees C). Tomato PE was rather heat labile at atmospheric pressure (inactivation in the temperature domain 57-65 degrees C), but it was very pressure resistant. Even at 900 MPa and 60 degrees C the inactivation was slower as compared to the same treatment at atmospheric pressure. At atmospheric pressure, optimal catalytic activity of PE was found at neutral pH and a temperature of 55 degrees C. Increasing pressure up to 300 MPa increased the enzyme activity as compared to atmospheric pressure. A maximal enzyme activity was found at 100-200 MPa combined with a temperature of 60-65 degrees C. The presence of Ca(2+) ions (60 mM) decreased the enzyme activity at atmospheric pressure in the temperature range 45-60 degrees C but increased enzyme activity at elevated pressure (up to 300 MPa). Maximal enzyme activity in the presence of Ca(2+) ions was noted at 200-300 MPa in combination with a temperature of 65-70 degrees C.     

Season and Nitrogen Effects on Activities of Three Hydrolytic Enzymes in Soils of the Gurbantunggut Desert,Northwest China

The activities of three extracellular hydrolytic enzymes, soil invertase, urease, and alkaline phosphatase (AlP), were measured across seasons and with the experimental addition of nitrogen (N) in the soil of the Gurbantunggut Desert, Northwest China. Seasonal fluctuations in hydrolytic enzyme activities were not correlated with seasonal variations in soil temperature, water content, pH, conductance, and organic carbon. Invertase and AlP activities increased with low rates of N addition, peaked at a N addition rate of 3.0 g N m^?2 y^?1, and then decreased at higher N addition rates. Urease activity decreased with increasing N addition. Higher organic matter content in the upper depths of soil resulted in higher hydrolytic enzyme activity at depths of 0–5 cm in soil samples and hydrolytic enzyme activity at that depth was more sensitive to N addition and seasonal environmental factors than that at depths of 5–10 cm in soil samples.     

Purification and characterization of trypsin from the spleen of tongol tuna (Thunnus tonggol)

Trypsin from tongol tuna (Thunnus tonggol) spleen was purified to 402-fold by ammonium sulfate precipitation, followed by a series of chromatographic separations. The molecular mass of trypsin was estimated to be 24 kDa by size-exclusion chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Trypsin appearing as a single band on native PAGE showed the maximal activity at pH 8.5 and 65 degrees C. It was stable in a wide pH range of 6-11 but unstable at the temperatures greater than 50 degrees C. The enzyme required calcium ion for thermal stability. The activity was strongly inhibited by 1.0 g/L soybean trypsin inhibitor and 5 mM TLCK and partially inhibited by 2 mM ethylenediaminetetraacetic acid. Activity was lowered with an increasing NaCl concentration (0-30%). The enzyme had a Km for Nalpha-p-tosyl-L-arginine methyl ester hydrochloride of 0.25 mM and a Kcat of 200 s-1. The N-terminal amino acid sequence of trypsin was determined as IVGGYECQAHSQPHQVSLNA and was very homologous to other trypsins.     

黄土高原油松根际土壤酶活性及真菌群落多样性研究——以黄龙山林场为例

为了解黄土高原油松林根际土壤酶活性和真菌群落多样性,本研究分析了陕西黄龙县不同样区油松根际土壤脲酶、碱性磷酸酶、多酚氧化酶和过氧化氢酶活性,并采用巢式PCR-变性梯度凝胶电泳(PCR-DGGE)技术研究了油松根际土壤中真菌群落多样性。结果表明,该地区油松根际真菌群落相似性较高,但受坡向、海拔、土壤水分及人类扰动等诸多因素的影响,不同样区的真菌群落多样性和土壤酶活性存在差异。油松根际各土壤酶活性均表现出坡顶样地高于坡底样地,阴面样地高于阳面样地,林区路旁样地由于采样环境不同于林中样地,酶活性介于其他样地之间;丰富度(S)、Shannon-Wiener指数(H)、Simpson指数(D)、均匀度指数(EH)分析表明,该区域油松根际土壤真菌群落多样性分布特征与酶活性分布特征相一致。相关性分析表明,除过氧化氢酶外,其余酶活性之间、以及与真菌多样性均呈显著正相关(p0.05);土壤含水量与真菌多样性和土壤酶活性除多酚氧化酶外均呈显著正相关(p0.05);而土壤p H与各种酶活性之间均未达显著相关水平(p0.05)。土壤含水量是影响该地区真菌群落多样性与土壤酶活性主要因素之一。     

水稻田土壤甲烷氧化活性及其环境影响因子的研究

报道环境因子土壤含水量、温度和pH对发育于河流沉积物母质的水稻田土黄松泥田土氧化外源甲烷活性影响的研究结果。表明土壤中存在有氧和无氧两个甲烷氧化系统。有氧甲烷氧化系统 (AMOS)最适条件下的氧化甲烷最大活性比无氧甲烷氧化系统(AAMOS)最适条件下的氧化甲烷最大活性高 1至 2倍。在土壤通气良好的条件下 ,AMOS占主导地位 ,在无氧或极微氧的土壤中 ,AAMOS起主要作用。影响活性的主要因子是土壤的分子氧含量、甲烷含量、水含量、温度和pH值。分子氧对AAMOS氧化甲烷的活性具有一定抑制作用 ,土壤中甲烷量和含水量对AAMOS氧化甲烷活性的影响比对AMOS氧化甲烷活性的影响更为强烈。土壤氧化甲烷的活性对温度较为敏感 ,其最适氧化甲烷的温度范围在 2 5～ 35℃之间。当土壤在 5 0℃培养的时间超过 6h后 ,土壤氧化外源甲烷的活性全部丧失 ,且不能在2 8℃下得到恢复。pH是另一个影响土壤氧化甲烷的重要环境因子。其最适pH范围在 6～ 7之间 ,pH低于 3或pH高于 9时 ,几乎完全丧失氧化外源甲烷的活性。     

Determination of the secondary structure of Kluyveromyces lactis beta-galactosidase by circular dichroism and its structure-activity relationship as a function of the pH

The secondary structure of Kluyveromyces lactis beta-galactosidase was determined by circular dichroism. It is mainly a beta-type protein, having 22% beta-turns, 14% parallel beta-sheet, 25% antiparallel beta-sheet, 34% unordered structure, and only 5% alpha-helix. The structure-activity relationship as a function of the pH was also studied. The pH conditions leading to the highest secondary structure content (100% ellipticity) of the enzyme was found at pH 7.0; at pH 6.5-7.0, the percent ellipticity decreased slightly, suggesting little structural change, but the activity decreased significantly, probably because of variations in critical residues. On the other hand, at pH's above 7.0, a more noticeable change in ellipticity was observed due to structural changes; the CD analysis showed a small increase in the helical content toward higher pH, whereas the maximum activity was found at pH 7.5, meaning that the changes produced in the secondary structure at this pH favored the interaction between the enzyme and the substrate.     

酸雨对木芙蓉幼苗光合作用及抗氧化酶活性的影响

以pH 5.6为对照,采用pH 4.0、pH 3.0、pH 2.0强度的酸雨对2年生木芙蓉进行人工模拟胁迫,研究酸雨胁迫对木芙蓉叶片可见伤害、质膜透性(Membrane Permeability,MP)、叶绿素(Chlorophyll,Chl)含量、抗氧化酶系统及气体交换参数的影响.研究结果表明,pH 2.0和pH 3...     

Influence of Jet‐Cooking Prowashonupana Barley Flour on Phenolic Composition,Antioxidant Activities,and Viscoelastic Properties

The objective was to study the influence of jet‐cooked Prowashonupana barley flour on total phenolic contents, antioxidant activities, water‐holding capacities, and viscoelastic properties. Barley flour was jet‐cooked without or with pH adjustment at 7, 9, or 11. Generally, the free phenolic content and antioxidant activity decreased after jet‐cooking, while the bound phenolic content and antioxidant significantly increased regardless of pH. Detectable levels of gallic acid, caffeic acid, ferulic acid, and p‐coumaroyl‐pentose in the jet‐cooked barley flour hydrolysates along with vitexin were found among 21 phenolics by LC‐ESI‐Q‐TOF‐MS analysis. Jet‐cooking at an elevated pH resulted in increased pasting viscosities. The oil content was decreased after jet‐cooking and continued to decrease with increased pH values. Jet cooking dramatically increased water holding capacity from 179% for unprocessed flour to 643% for jet‐cooked flour without pH adjustment, and water‐holding capacity was greatly increased to 914% by jet‐cooking at pH 11. The combination of jet‐cooking and pH adjustment had tremendous influence on water‐holding and pasting properties. This increase in functionality should contribute to food applications such as bakery and frozen products because of the release of the bound phenolic content, antioxidant activities, and improved water‐holding and pasting abilities.     

水盐梯度对滨海湿地土壤养分指标和酶活性的影响

[目的]研究海水入侵对滨海湿地土壤性质的影响,为分析水盐梯度对土壤养分指标和酶活性的影响机制提供依据。[方法]采集胶州湾滨海湿地表层土壤并设计室内模拟试验,测定不同水盐梯度上的土壤养分指标和酶活性。[结果]盐分和水分对土壤pH值和容重(BD)的影响显著;土壤有机质(TOM)、氨氮(NH_4~+-N)、速效磷(AP)、速效钾(AK)、蔗糖酶(SA)、脲酶(UA)、碱性磷酸酶(APA)均随水梯度的增加表现为先升高后降低的趋势,在30%水梯度时达到最高值;土壤TOM,AP,AK,SA,UA,APA均随盐梯度的增加而降低,NH_4~+-N随盐梯度的增加而增加。土壤SA与TOM,AP,AK存在显著正相关关系;APA与TOM,AP,AK,BD显著正相关;UA与pH值,BD显著正相关,与NH_4~+-N具有一定的相关性。[结论]在一定范围内,土壤中水分过高或过低、盐分增加均会对土壤养分含量和酶活性产生抑制作用;土壤养分和酶活性之间存在密切的相关关系。     

Interaction of horseradish peroxidase with montmorillonite homoionic to Na+ and Ca2+: effects on enzymatic activity and microbial degradation

The adsorption, desorption, catalytic activity, and susceptibility to microbial degradation of the enzyme horseradish peroxidase (HRP E.C. 1.11.1.7), on Wyoming montmorillonite (M) homoionic to Na⁺ or Ca²⁺ were investigated. Adsorption at equilibrium was reached after 1 h of contact between the clay and HRP. The adsorption isotherms were of the L type and fitted the Freundlich equation on M-Na and the Langmuir equation on M-Ca. Adsorption was greater on M-Na than on M-Ca and was maximal at pH 3.0, i.e., below the isoelectric point (pI=pH 9) of the protein. Only 10–25% of HRP was desorbed from the equilibrium M-Na-HRP complexes, whereas 20–30% was desorbed from the equilibrium M-Ca-HRP complexes with 4–7 washes with double distilled water. HRP partially penetrated the interlayers of M-Na and M-Ca, but complete intercalation was observed only at pH 3. The enzymatic activity of HRP measured immediately after the preparation of the complexes at all concentrations was greatly reduced when bound on M-Na (about 90%), regardless of the loading of HRP. The reduction in activity of M-Ca-HRP was related to the amount of bound protein (no reduction for the highest and 60% for the lowest amount bound). After 24 h, pure HRP in dilute solution lost about 10% of its catalytic activity daily, whereas when bound on M-Ca, a greater reduction was observed (about 30% for the highest and 60% for the lowest amount bound). FT-IR analyses indicated only small changes in the secondary structure of HRP as a result of binding on the clays. Electronic absorption spectra in the UV region of bound HRP did not show the typical ‘red-shift’ of the Soret band that usually results from binding of HRP with its substrate. Consequently, the reduction in the activity of bound HRP was probably the result of the inaccessibility and/or of modifications of the active center of HRP for its substrate. The availability of HRP bound on M-Na as a source of carbon and/or nitrogen for soil microorganisms was reduced by 90% in comparison with the free enzyme.     

Spatial variation of ammonia volatilization from soil and its scale‐dependent correlation with soil properties

Quantitative predictions of ammonia volatilization from soil are useful to environmental managers and policy makers and empirical models have been used with some success. Spatial analysis of the soil properties and their relationship to the ammonia volatilization process is important as predictions will be required at disparate scales from the field to the catchment and beyond. These relationships are known to change across scales and this may affect the performance of an empirical model. This study is concerned with the variation of ammonia volatilization and some controlling soil properties: bulk density, volumetric water content, pH, CEC, soil pH buffer power, and urease activity, over distances of 2, 50, 500, and >2000 m. We sampled a 16 km × 16 km region in eastern England and analyzed the results by a nested analysis of (co)variance, from which variance components and correlations for each scale were obtained. The overall correlations between ammonia volatilization and the soil properties were generally weak: –0.09 for bulk density, 0.04 for volumetric water content, –0.22 for CEC, –0.08 for urease activity, –0.22 for pH and 0.18 for the soil pH buffer power. Variation in ammonia volatilization was scale‐dependent, with substantial variance components at the 2‐ and 500‐m scales. The results from the analysis of covariance show that the relationships between ammonia volatilization and soil properties are complex. At the >2000 m scale, ammonia volatilization was strongly correlated with pH (–0.82) and CEC (–0.55), which is probably the result of differences in parent material. We also observed weaker correlations at the 500‐m scale with bulk density (–0.61), volumetric water content (0.48), urease activity (–0.42), pH (–0.55) and soil pH buffer power (0.38). Nested analysis showed that overall correlations may mask relationships at scales of interest and the effect of soil variables on these soil processes is scale‐dependent.     

Changes in Nixtamalized Corn Flour Dependent on Postcooking Steeping Time

We studied the effect of steeping time on various physical and chemical properties of maize flour prepared by the traditional nixtamalization process as well as in oversaturated calcium ion conditions. The calcium content of the corn flour was measured by atomic absorption spectroscopy and was correlated with X‐ray diffraction, viscosity, and pH measurements. Calcium content of the flour showed a nonlinear dependence on steeping time, with a local calcium maximum occurring at ≈7 hr. The pH level of the corn flour increased with steeping time, thus roughly following the time trend shown by the steeping time dependence of the calcium content. Flour crystallinity and peak viscosity of water suspensions of the flour reached maximal values at ≈7–9 hr of steeping, in agreement with manufacturing experience showing that these are appropriate steeping times to prepare tortillas with the desirable rheological and organoleptic properties.     

Effect of high-pressure treatment on lipoxygenase activity

Solutions of commercial soybean lipoxygenase (100 microgram/ML in 0.2 M citrate-phosphate and 0.2 M Tris buffer were subjected to pressures of 0.1, 200, 400, and 600 MPa for 20 mm. The enzyme was stable at atmospheric pressure (0.1 MPa) over a wide pH range (5-9). In citrate phosphate buffer, the enzyme had maximum stability over the pH range 58 in untreated samples and after treatment at 200 MPa, but with increasing pressure, the pH stability range become narrower and centered around pH 78. The enzyme was more sensitive to acid than alkali, and at pH 9, it lost virtually all activity after pressurization at 600 MPa for 20 mm in both buffers. The activity of the crude enzyme extracted from tomatoes treated at 200 and 300 MPa for 10 mm was not significantly different from that of the untreated tomatoes, while a pressure of 400 MPa for 10 mm caused a significant decrease in activity and treatment at 600 MPa led to complete and irreversible activity loss. Compared to unpressurized tomatoes, treatment at 600 MPa gave significantly reduced levels of hexanal, cis-3-hexenal, and trans-2-hexenal, which are important contributors to "fresh" tomato flavor, and this was attributed to the inactivation of lipoxygenase.     

Characterization of a thermostable extracellular beta-glucosidase with activities of exoglucanase and transglycosylation from Paecilomyces thermophila

The purification and characterization of a novel extracellular beta-glucosidase from Paecilomyces thermophila J18 was studied. The beta-glucosidase was purified to 105-fold apparent homogeneity with a recovery yield of 21.7% by DEAE 52 and Sephacryl S-200 chromatographies. Its molecular masses were 116 and 197 kDa when detected by SDS-PAGE and gel filtration, respectively. It was a homodimeric glycoprotein with a carbohydrate content of 82.3%. The purified enzyme exhibited an optimal activity at 75 degrees C and pH 6.2. It was stable up to 65 degrees C and in the pH range of 5.0-8.5. The enzyme exhibited a broad substrate specificity and significantly hydrolyzed p-nitrophenyl-beta- d-glucopyranoside ( pNPG), cellobiose, gentiobiose, sophorose, amygdalin, salicin, daidzin, and genistin. Moreover, it displayed substantial activity on beta-glucans such as laminarin and lichenan, indicating that the enzyme has some exoglucanase activity. The rate of glucose released by the purified enzyme from cellooligosaccharides with a degree of polymerization (DP) ranging between 2 and 5 decreased with increasing chain length. Glucose and glucono-delta-lactone inhibited the beta-glucosidase competitively with Ki values of 73 and 0.49 mM, respectively. The beta-glucosidase hydrolyzed pNPG, cellobiose, gentiobiose, sophorose, salicin, and amygdalin, exhibiting apparent Km values of 0.26, 0.65, 0.77, 1.06, 1.39, and 1.45 mM, respectively. Besides, the enzyme showed transglycosylation activity, producing oligosaccharides with higher DP than the substrates when cellooligosaccharides were hydrolyzed. These properties make this beta-glucosidase useful for various biotechnological applications.