Secretion of acid phosphatase from extraradical hyphae of the arbuscular mycorrhizal fungus Rhizophagus clarus is regulated in response to phosphate availability

Arbuscular mycorrhizal (AM) fungi increase phosphate (P) uptake by plants. Organic phosphate comprises 30-80% of total P in most agricultural soils. Some plants can utilize organic phosphate by secreting acid phosphatase (ACP) from their roots, especially under low P conditions. Although secretion of ACP from extraradical hyphae of AM fungi has been reported, the specific factors that affect the secretion of ACP are unknown. The objective of the present study was to investigate whether secretion of ACP from extraradical hyphae is induced by low P conditions. First, specimens of Allium fistulosum were either inoculated with the AM fungus Rhizophagus clarus strain CK001 or remained uninoculated and were grown in soil with 0.5 g P₂O₅ kg^-1 soil or without P fertilization using two-compartment pots. Soil solution was collected using mullite ceramic tubes 45 days after sowing. The soil solution was analyzed for ACP activity by using p-nitrophenylphosphate. Second, Ri T-DNA transformed roots (i.e., hairy roots) of Linum usitatissimum inoculated with R. clarus were grown on solid minimal media with two P levels applied (3 and 30 μM P) using two-compartment Petri dishes under in vitro conditions. Hyphal exudates, extraradical hyphae, and hairy roots were collected and analyzed for ACP activity. ACP activity in the soil solution of the hyphal compartment in the A. fistulosum inoculation treatment was higher without P fertilization than with P fertilization. AM colonization also was higher without P fertilization than with P fertilization. In the in vitro two-compartment culture, ACP activity of hyphal exudates and extraradical hyphae were higher under the 3-μM treatment than under the 30-μM treatment. These findings suggest that the secretion of ACP from the extraradical hyphae of R. clarus into the hyphosphere is promoted under low P conditions.

Competitive redox reaction of Au-NCs/MnO2 nanocomposite: Toward colorimetric and fluorometric detection of acid phosphatase as an indicator of soil cadmium contamination

In this study, by rational regulating the competitive redox reaction of Au-NCs/MnO₂ nanocomposite between the dye indigo carmine (IC) and the enzymatic product L-ascorbic acid (AA), we have established a colorimetric and fluorometric double-channel responsive assay for acid phosphatase (ACP), which could serve as an indicator of soil cadmium (Cd) contamination. Initially, the gold nanoclusters (Au-NCs) were added to the suspension of MnO₂ nanosheets to form Au-NCs/MnO₂ nanocomposite with enhanced oxidative degradation ability. When IC was subsequently added, the blue color of IC faded due to oxidative degradation, and the mixture showed the yellow color of Au-NCs/MnO₂ nanocomposite. Meanwhile, based on the inner filter effect (IFE), the fluorescence of Au-NCs was suppressed by MnO₂ nanosheets during this process. However, with the presence of AA, hydrolyzed from L-ascorbic-2-phosphate (AAP) by ACP, the MnO₂ nanosheets in Au-NCs/MnO₂ nanocomposite were reduced to Mn²⁺ immediately. As a consequence, IC remained its blue color, in the meantime, the fluorescence of Au-NCs recovered, which essentially constituted a new mechanism for ACP detection with colorimetric and fluorometric double-channel response. With the method we developed, soil ACP activity can either be directly visualized by bare eyes or detected reliably through double channels. Furthermore, the dynamic changes of ACP activity during soil Cd contamination could also be monitored; the sharp increase of ACP activity at an appropriate time point could serve as a unique alarm for cadmium (Cd) contamination in soil, which is of great importance for soil quality evaluation and ecological risk assessment.

Comparative analysis of β-hexosaminidase and acid phosphatase from Hydra vulgaris Ind-Pune, H. vulgaris Naukuchiatal and H. magnipapillata sf-1: Localization studies of acid phosphatase and β-hexosaminidase from H. vulgaris Ind-Pune

The present report describes a comprehensive study on comparative biochemical characterization of two lysosomal enzymes, acid phosphatase and β-hexosaminidase in three different strains of Hydra; Hydra vulgaris Ind-Pune, H. vulgaris Naukuchiatal and H. magnipapillata sf-1 (self-feeder-1). Since morphology and habitat of Hydra effect lysosomal enzymes and their response to environmental pollutants, it would be interesting to identify them in different Hydra strains so as to use them as toxicity testing. Preliminary studies revealed a differential expression of acid phosphatase, β-hexosaminidase and β-glucuronidase in three Hydra strains. Expression of all three lysosomal enzymes in H. vulgaris Ind-Pune was low in comparison to H. vulgaris Naukuchiatal and H. magnipapillata sf-1, while their expression is comparable in H. vulgaris Naukuchiatal and H. magnipapillata sf-1. The Michaelis-Menten (K_M) values for lysosomal β-hexosaminidase using 4-nitrophenyl N-acetyl-β-D-glucosaminide as substrate were found to be 1.3 mM, 1.1 mM and 0.8 mM, respectively for H. vulgaris Ind-Pune, H. vulgaris Naukuchiatal and H. magnipapillata sf-1. For acid phosphatase using 4-nitrophenyl-phosphate as substrate, the K_M values were 0.38 mM, 1.2 mM and 0.52 mM respectively, for H. vulgaris Ind-Pune, H. vulgaris Naukuchiatal and sf-1 strains. The optimum temperature for β-hexosaminidase was 60 °C for H. vulgaris Ind-Pune, while 50 °C was observed for H. vulgaris Naukuchiatal and sf-1 strains. The optimum pH for β-hexosaminidase was found to be 6.0 for H. vulgaris Ind-Pune and H. vulgaris Naukuchiatal, and 5.0 for sf-1. The optimum temperature and pH of acid phosphatase was similar in all three strains, viz., 40 °C and 3.0, respectively. Preliminary localization studies using whole mount in situ hybridization revealed predominant endodermal expression of three enzymes in H. vulgaris Ind-Pune. Our results thus support the conservation of lysosomal hydrolases in Hydra.

Carbon dots as an "on-off-on" fluorescent probe for detection of Cu(II) ion, ascorbic acid, and acid phosphatase

Carbon dot (CD)-based fluorescent probes have been widely exploited; however, multi-component detection using CDs without tedious surface modification is always a challenging task. Here, we develop a convenient and simple CD-based "on-off-on" fluorescent probe for detection of copper(II) ion (Cu²⁺), ascorbic acid (AA), and acid phosphatase (ACP). Cu²⁺ leads to the fluorescence quenching of CDs. The limit of detection (LOD) for Cu²⁺ is 2.4 μM. When AA is added into the CDs + Cu²⁺ solution, Cu²⁺ is reduced by AA to Cu⁺, causing the fluorescence recovery of CDs. The fluorescent intensity linearly correlates with the concentration of AA in the range of 100-2800 μM with LOD of 60 μM. Besides, the probe has potential application for detection of AA in real samples such as VC tablets, orange juice, and fresh orange. The probe can also indirectly detect ACP that enzymatically hydrolyzes ascorbic acid-phosphate (AAP) to produce AA. This work expands the application of CDs in the multi-component detection and provides a facile fluorescent probe for detection of AA in real samples. Graphical abstract.

Detecting acid phosphatase enzymatic activity with phenol as a chemical exchange saturation transfer magnetic resonance imaging contrast agent (PhenolCEST MRI)

Phenol contains an exchangeable hydroxyl proton resonant at 4.8 ppm from the resonance frequency of water in the ¹H nuclear magnetic resonance (¹H NMR) spectrum, enabling itself to be detected at sub-mM concentration by either chemical exchange saturation transfer magnetic resonance imaging (CEST MRI) or exchange-based T₂ relaxation enhancement (T_2ex) effect under acidic and basic conditions, respectively. We recently investigated the T_2ex effects of phenol and its derivatives, but the CEST characteristics of phenols are unknown in detail, and no study on using the natural CEST MRI effects of phenol for detecting enzymatic activity has been conducted. Herein, on the basis of the inherent CEST MR property of phenol, namely phenolCEST, we developed the first MRI approach to detect acid phosphatase (AcP) enzymatic activity. Upon the activity of AcP at pH = 5.0, non-CEST-detectable enzyme substrate phenyl phosphate was converted to CEST-detectable phenol, providing a simple way to quantify AcP activity directly without the need for a second signalling probe. We showed the application of this phenolCEST biosensor for measuring AcP activity in both enzyme solutions and cell lysates of prostate cells. This work opens a door for the utilization of phenolCEST MRI technique in sensor design and development.

Determination of prostate cancer biomarker acid phosphatase at a copper phthalocyanine-modified screen printed gold transducer

In this work, a novel sensor based on immobilised copper phthalocyanine, 2,9,16,23-tetracarboxylic acid-polyacrylamide (Cu(II)TC Pc-PAA) was developed for determination of acid phosphatase (ACP) levels in nanomolar quantities. Detection was based on the measurement of enzymatically generated phosphate, with initial studies focused on phosphate detection at a Cu(II)TC Pc-PAA modified screen-printed gold transducer. The sensor was characterised in relation to operational performance (pH, response time, stability, linearity, and sensitivity) and common anionic interferents (nitrate, sulphate, chloride, and perchlorate). The functionalised surface also facilitated rapid detection of the enzyme bi-product 2-naphthol over the range 5-3000 μM. Quantitation of ACP was demonstrated, realising a linear response range of 0.5-20 nM and LOD of 0.5 nM, which is within the clinical range for this prostate cancer biomarker.

The acid phosphatase Pho5 of Saccharomyces cerevisiae is not involved in polyphosphate breakdown

Inorganic polyphosphate is involved in architecture and functioning of yeast cell wall. The strain of Saccharomyces cerevisiae constitutively overexpressing acid phosphatase Pho5 was constructed for studying the Pho5 properties and its possible participation in polyphosphate metabolism. The parent strain was transformed by the vector carrying the PHO5 gene under a strong constitutive promoter of glyceraldehyde-3-phosphate dehydrogenase of S. cerevisiae. The culture liquid and biomass of transformant strain contained approximately equal total acid phosphatase activity. The levels of acid phosphatase activity associated with the cell wall and culture liquid increased in the transformant strain compared to the parent strain ~ 10- and 20-fold, respectively. The Pho5 preparation (specific activity of 46 U/mg protein and yield of 95 U/L) was obtained from culture liquid of overproducing strain. The overproducing strain had no changes in polyphosphate level. The activity of Pho5 with long-chained polyP was negligible. We concluded that Pho5 is not involved in polyphosphate metabolism. Purified Pho5 showed a similar activity with p-nitrophenylphosphate, ATP, ADP, glycerophosphate, and glucose-6-phosphate. The substrate specificity of Pho5 and its extracellular localization suggest its function: the hydrolysis of organic compounds with phosphoester bonds at phosphate limitation.

Effects of long term oral acrylamide administration on alpha naphthyl acetate esterase and acid phosphatase activities in the peripheral blood lymphocytes of rats

Acrylamide is an important industrial chemical; it also is formed in starch-rich foodstuffs during baking, frying and roasting. Most acrylamide exposure occurs by ingestion of processed foods. We investigated possible immunotoxic effects of extended administration of low doses of acrylamide in rats. To do this, we measured alpha-naphthyl acetate esterase (ANAE) and acid phosphatase (ACP-ase) activities in peripheral blood lymphocytes. Male and female weanling Wistar rats were administered 2 or 5 mg acrylamide/kg/day in drinking water for 90 days. Peripheral blood was sampled at the end of the administration period. We found ANAE staining in eosinophils and T-lymphocytes, but not in monocytes, platelets, B-lymphocytes and neutrophils. ACP-ase was found in B-lymphocytes. We found a significant reduction of the ratio of ANAE:ACP-ase in lymphocytes of the experimental animals compared to controls. We found no statistically significant differences between the doses or sexes. We found that acrylamide ingested in processed foods might affect the immune system adversely by decreasing the population of mature T- and B-lymphocytes.

The mRNA expression and enzymatic activity of three enzymes during embryonic development of the hard tick Haemaphysalis longicornis

Background

Three main enzymes including cathepsin B, cathepsin D and acid phosphatase are involved in vitellin degradation, which is a major biochemical event of the embryonic development and can provide nutrients and metabolites for tick embryos. In the present study, the mRNA expression profiles and enzymatic activity of cathepsin B, cathepsin D and acid phosphatase were investigated during embryonic development in the tick Haemaphysalis longicornis.

Results

The results revealed that all three enzymes were expressed throughout embryonic development. Both cathepsin B and acid phosphatase transcripts were accumulated during the first four days. Cathepsin B reached its highest expression on day 5, whereas the peak expression of acid phosphatase and cathepsin D occurred on day 11. The highest activity of cathepsin B was observed on the first day of egg development, whereas cathepsin D reached its highest activity on day 13. Acid phosphatase activity increased gradually during the first five days and then remained stable until the end of egg development.

Conclusions

Three enzymes were expressed and activated in eggs, and also presented different dynamic changes with the development of embryos. The profiles of both mRNA expression and enzymatic activity of these enzymes indicate that they are controlled orderly and play multiple roles during embryonic development in ticks.

Changes in P accumulation, tissue P fractions and acid phosphatase activity of Pilea sinofasciata in poultry manure-impacted soil

Pilea sinofasciata is a promising phytoextraction material to remove excess phosphorus (P) from manure-impacted soil. However, little information is available on its physiological response to animal manure treatments. Here, P accumulation, tissue P fractions and acid phosphatase activity were investigated in a mining ecotype (ME) and a non-mining ecotype (NME) of P. sinofasciata at different poultry manure (PM) treatments (0, 25, 50, 75, 100 and 125 g kg^-1). Biomass and P accumulation of the ME increased up to 50 g kg^-1, after which they significantly decreased; while P accumulation of the NME increased up to 100 g kg^-1. But, shoot and root P accumulation of the ME were significantly higher than those of the NME at all PM treatments, showing 1.13-2.92 and 1.11-2.89 times higher values, respectively. Inorganic P and nucleic P dominated in tissues of both ecotypes. Besides, the ME maintained higher concentrations of inorganic P and ester P in leaves and ester P, nucleic P and residual P in roots than the NME. Acid phosphatase activity in leaves and roots increased by increasing PM treatments, except in root at 125 g kg^-1. Acid phosphatase activity in leaves of the ME was positively correlated with concentrations of inorganic P, ester P and nucleic P, while that of the NME only correlated with inorganic P concentration. Probably, the optimized P fractions allocation and higher tissue acid phosphatase allow the ME to grow well and efficiently accumulate P in PM-impacted soil.

A novel fluorescence "turn off-on" nanosensor for sensitivity detection acid phosphatase and inhibitor based on glutathione-functionalized graphene quantum dots

In this paper, we developed a label-free and sensitive fluorescence sensor for acid phosphatase (ACP) and its inhibitor parathion-methyl (PM) detection based on glutathione-functionalized graphene quantum dots (GQDs@GSH). Upon addition of MnO₂ nanosheets, the fluorescence of GQDs@GSH could be efficiently quenched via a fluorescence resonance energy transfer. ACP could easily catalyze the hydrolysis of L-Ascorbic acid-2-phosphate (AAP) to ascorbic acid (AA), which could reduce MnO₂ nanosheets to Mn²⁺ in acidic environment, leading to dramatically increase of the fluorescence intensity of GQDs@GSH. Quantitative detection of ACP in a broad range from 0.1 to 9 mU mL^-1 with a detection limit of 0.027 mU mL^-1 could be achieved. The feasibility of the proposed sensor in real samples analysis was also studied and satisfactory results were obtained. Furthermore, the fluorescence assay strategy could also be used for the detection of parathion-methyl (PM) as ACP inhibitor.

Peptiduria: a potential early predictor of diabetic kidney disease

BACKGROUND

To protect the kidney effectively with medication in type 2 diabetics, it is crucial to identify such at-risk patients early for treatment. We investigated whether peptiduria precedes proteinuria (the earliest urinary marker in our model), and thereby serve as an early predictor of diabetic nephropathy.

METHODS

A longitudinal study was performed in a rat model of diabetic nephropathy. Peptides, defined as degradation products of proteins of < 13 kD size, were quantified by a previously validated method using a combination of Lowry and Biorad protein assays. Peptides in urine were also confirmed by chromatographically separating low molecular weight fractions from urine and quantifying albumin fragments in these fractions by enzyme immunoassay. Also, the mechanism of peptiduria was addressed by measuring acid phosphatase, a marker of lysosomal activity, in urine and on kidney sections (histochemically).

RESULTS

In rats with diabetic nephropathy, proteinuria occurred after 12 weeks of diabetes, while peptiduria occurred as early as 2 weeks after diabetes. Peptiduria was confirmed by showing that the chromatographically separated low molecular weight fractions of urine containing albumin fragments is in proportion to the level of peptiduria. The time course of peptiduria paralleled the increase in urinary acid phosphatase suggesting that the mechanism of early peptiduria could be due to upregulation of lysosomal enzyme activity in the tubules.

CONCLUSIONS

Our results showing that peptiduria precedes proteinuria in diabetic nephropathy provide a compelling rationale to perform a prospective human clinical trial to investigate whether peptiduria can serve as an early predictor of diabetic nephropathy.

A pilot study: The effects of repeat washing and fabric type on the detection of seminal fluid and spermatozoa

In sexual assault cases and more specifically those involving childhood sexual abuse (CSA), victims may have had their potentially semen-stained clothing washed multiple times before a criminal investigation commences. Although it has been previously demonstrated that spermatozoa persist on cotton clothing following a single wash cycle, items of clothing washed multiple times are not routinely examined in these cases because of the assumption that the laundering process would have removed all seminal fluid and spermatozoa. The aim of this study was to examine the persistence of seminal fluid and spermatozoa on a range of fabric types including cotton, nylon, terry towel (100% cotton), polyester fleece, satin and lace which were laundered up to six times. Three techniques were used for the detection of seminal fluid and spermatozoa: an alternative light source, acid phosphatase test and microscopy. The study demonstrated that spermatozoa persisted on cotton and terry towel following six wash cycles. This data emphasises the need to recover and examine items of clothing and bedding of victims for semen, even if the item has been washed multiple times.

Probing the toxic mechanism of bisphenol A with acid phosphatase at the molecular level

As an endocrine-disrupting chemical, bisphenol A (BPA), can affect normal endocrine function of hormone. This paper studied the toxic effect of BPA on acid phosphatase at the molecular level by multi-spectroscopic measurements, molecular docking, and enzyme activity experiment. BPA could enhance the fluorescence intensity, change the structure, and cause an increased hydrophobicity of acid phosphatase. Hydrogen bond interaction and van der Waals forces were the main forces to generate the BPA-acid phosphatase complex on account of the negative ΔH (- 36.92 kJ mol^-1) and ΔS (- 50.78 J mol^-1 K^-1). BPA led to the loosening and unfolding of protein structure and extending the peptide strands, as revealed by UV-vis absorption and CD spectra. Based on the enzyme activity experiment, BPA could decrease the activity of the acid phosphatase by entering the active site of the enzyme. The molecular docking model showed that BPA could bind into the cavity of acid phosphatase and interact with Tyr A252 and a hydrogen bond (1.47 Å) was formed in the binding process. This work suggested the structures and functions of acid phosphatase were both affected by BPA.

Methods for Monitoring Autophagy in Silkworm Organs

In holometabolous insects, various larval organs are remodeled by autophagy during metamorphosis. Although moths and butterflies are among the first animal models in which this self-eating process was described, only in recent years autophagy has been analyzed in detail in these insects. In particular, the silkworm Bombyx mori, which represents a well-studied model among Lepidoptera, provides a wide repertoire of cellular and molecular tools useful for studying the occurrence of autophagy and for evaluating its role in postembryonic development. Here, we describe some morphological, biochemical, and molecular methods to monitor autophagy in silkworm organs.

Identification and Characterization of Memecylon Species Using Isozyme Profiling

Background:

The protein/isozyme fingerprint is useful in differentiating the species and acts as a biochemical marker for identification and systematic studies of medicinal plant species.

Objective:

In the present study, protein and isozyme profiles for peroxidase, esterase, acid phosphatase, polyphenol oxidase, alcohol dehydrogenase, and alkaline phosphatase of five species of Memecylon (Melastomataceae), Memecylon umbellatum, Memecylon edule, Memecylon talbotianum, Memecylon malabaricum, and Memecylon wightii were investigated.

Materials and Methods:

Fresh leaves were used to prepare crude enzyme extract for analyzing the five enzymes isozyme variations. Separation of isozymes was carried out using polyacrylamide gel electrophoresis (PAGE) and the banding patterns of protein were scored. Pair-wise comparisons of genotypes, based on the presence or absence of unique and shared polymorphic products, were used to regenerate similarity coefficients. The similarity coefficients were then used to construct dendrograms, using the unweighted pair group method with arithmetic averages.

Results:

A total of 50 bands with various Rf values and molecular weight were obtained through PAGE analysis. Among the five Memecylon species, more number of bands was produced in M. wightii and less number of bands was observed in M. edule. The results of similarity indices grouped M. malabaricum and M. wightii in one cluster with 98% similarity and M. umbellatum, M. edule, and M. talbotianum are grouped in another cluster with 79% similarity showing close genetic similarities which is in accordance with the morphological identification of Memecylon species.

Conclusion:

The protein/isozyme fingerprint is useful in differentiating the species and acts as a biochemical marker for identification of Memecylon species.

SUMMARY

Biochemical characterization of Memecylon species was evaluated by SDS-PAGE of extracted protein and isozyme profiling on native PAGE.

After electrophoresis, each gel was stained with specific stains. Genetic distance relationships were evaluated based on the banding patterns of protein on isozymes.

Unique banding pattern of esterase, peroxidase, acid phosphatase, alcohol dehydrogenase and polyphenol oxidase are observed in all the five species of Memecylon, which represent the fingerprint of Memecylon species.

SDS-PAGE and isozyme profiling of five Memecylon species revealed that M. malabaricum and M. wightii grouped in one cluster and M. umbellatum, M. edule and M. talbotianum grouped in another cluster showing close genetic similarities which is in accordance with the morphological identification of Memecylon species.

This is the first report on the comparison of protein and isozyme profile of five different Memecylon species.

Abbreviations Used: SDS-PAGE: Sodium docecyl sulfate polyacrylamide gel electrophoresis; NTSYS PC2: Numerical taxonomy system, version 2.2 for Windows XP, Vista, Win7, Win 8 and Win10 including 64 bit

Purification and characterization of acid phosphatase from Macrotyloma uiflorum seeds

Acid phosphatases play a crucial role in food processing industries to reduce phosphate content of food. Here in acid phosphatase from the seeds of Macrotyloma uniflorum has been purified to homogeneity using UNOsphere-S cation exchange chromatography followed by gel filtration with 81.85 fold purification. Molecular weight of purified enzyme was 55,000 (± 1040) Daltons under physiological conditions. It was a heterodimer of subunits having molecular weights 27,093 and 28,241 Daltons as determined by MALDI-TOF analysis. The optimum pH and temperature for the purified enzyme was 5.0 and 50 °C respectively. The enzyme was stable in the pH range 3.5-5.5 and showed temperature stability up to 60 °C. Substrate specificity of enzyme was checked with different substrates namely, p-nitrophenyl phosphate (p-NPP), ATP, ADP, glucose 6-phosphate, glucose-1-phosphate, fructose 6-phosphate, phenyl phosphate, α-naphthyl-phosphate, pyridoxyl phosphate and β-glycerophosphate. Enzyme showed high substrate specificity towards p-NPP, phenyl phosphate, ATP and α-naphthyl phosphate. K_m and V_max of enzyme were found to be 0.934 mM and 1.333 mM/min respectively with respect to p-NPP as a substrate. Chemical modification studies showed that tryptophan was present at the active site of the enzyme.

The 'known' genetic potential for microbial communities to degrade organic phosphorus is reduced in low-pH soils

In soil, bioavailable inorganic orthophosphate is found at low concentrations and thus limits biological growth. To overcome this phosphorus scarcity, plants and bacteria secrete numerous enzymes, namely acid and alkaline phosphatases, which cleave orthophosphate from various organic phosphorus substrates. Using profile hidden Markov modeling approaches, we investigated the abundance of various non specific phosphatases, both acid and alkaline, in metagenomes retrieved from soils with contrasting pH regimes. This analysis uncovered a marked reduction in the abundance and diversity of various alkaline phosphatases in low-pH soils that was not counterbalanced by an increase in acid phosphatases. Furthermore, it was also discovered that only half of the bacterial strains from different phyla deposited in the Integrated Microbial Genomes database harbor alkaline phosphatases. Taken together, our data suggests that these 'phosphatase lacking' isolates likely increase in low-pH soils and future research should ascertain how these bacteria overcome phosphorus scarcity.

Dissipation of S-metolachlor in plant and soil and effect on enzymatic activities

The present study aimed at evaluating the dissipation of S-metolachlor (S-MET) at three doses in maize growing on diverse physico-chemical properties of soil. The effect of herbicide on dehydrogenase (DHA) and acid phosphatase (ACP) activity was estimated. A modified QuEChERS method using LC-MS/MS has been developed. The limit of quantification (0.001 mg kg^-1) and detection (0.0005 mg kg^-1) were very low for soil and maize samples. The mean recoveries and RSDs for the six spiked levels (0.001-0.5 mg kg^-1) were 91.3 and 5.8%. The biggest differences in concentration of S-MET in maize were observed between the 28th and 63rd days. The dissipation of S-MET in the alkaline soil was the slowest between the 2nd and 7th days, and in the acidic soil between the 5th and 11th days. DT₅₀ of S-MET calculated according to the first-order kinetics model was 11.1-14.7 days (soil) and 9.6-13.9 days (maize). The enzymatic activity of soil was higher in the acidic environment. One observed the significant positive correlation of ACP with pH of soil and contents of potassium and magnesium and negative with contents of phosphorus and organic carbon. The results indicated that at harvest time, the residues of S-MET in maize were well below the safety limit for maize. The findings of this study will foster the research on main parameters influencing the dissipation in maize ecosystems.

Phylogenetic distribution, biogeography and the effects of land management upon bacterial non-specific Acid phosphatase Gene diversity and abundance

BACKGROUND AND AIMS

Bacterial Non-Specific Acid Phosphatase (NSAP) enzymes are capable of dephosphorylating diverse organic phosphoesters but are rarely studied: their distribution in natural and managed environments is poorly understood. The aim of this study was to generate new insight into the environmental distribution of NSAPs and establish their potential global relevance to cycling of organic phosphorus.

METHODS

We employed bioinformatic tools to determine NSAP diversity and subcellular localization in microbial genomes; used the corresponding NSAP gene sequences to census metagenomes from diverse ecosystems; studied the effect of long-term land management upon NSAP diversity and abundance.

RESULTS

Periplasmic class B NSAPs are poorly represented in marine and terrestrial environments, reflecting their association with enteric and pathogenic bacteria. Periplasmic class A and outer membrane-associated class C NSAPs are cosmopolitan. NSAPs are more abundant in marine than terrestrial ecosystems and class C more abundant than class A genes, except in an acidic peat where class A genes dominate. A clear effect of land management upon gene abundance was identified.

CONCLUSIONS

NSAP genes are cosmopolitan. Class C genes are more widely distributed: their association with the outer-membrane of cells gives them a clear role in the cycling of organic phosphorus, particularly in soils.

OsPAP26 Encodes a Major Purple Acid Phosphatase and Regulates Phosphate Remobilization in Rice

During phosphate (Pi) starvation or leaf senescence, the accumulation of intracellular and extracellular purple acid phosphatases (PAPs) increases in plants in order to scavenge organic phosphorus (P). In this study, we demonstrated that a PAP-encoding gene in rice, OsPAP26, is constitutively expressed in all tissues. While the abundance of OsPAP26 transcript is not affected by Pi supply, it is up-regulated during leaf senescence. Furthermore, Pi deprivation and leaf senescence greatly increased the abundance of OsPAP26 protein. Overexpression or RNA interference (RNAi) of OsPAP26 in transgenic rice significantly increased or reduced APase activities, respectively, in leaves, roots and growth medium. Compared with wild-type (WT) plants, Pi concentrations of OsPAP26-overexpressing plants increased in the non-senescing leaves and decreased in the senescing leaves. The increased remobilization of Pi from the senescing leaves to non-senescing leaves in the OsPAP26-overexpressing plants resulted in better growth performance when plants were grown in Pi-depleted condition. In contrast, OsPAP26-RNAi plants retained more Pi in the senescing leaves, and were more sensitive to Pi starvation stress. OsPAP26 was found to localize to the apoplast of rice cells. Western blot analysis of protein extracts from callus growth medium confirmed that OsPAP26 is a secreted PAP. OsPAP26-overexpressing plants were capable of converting more ATP into inorganic Pi in the growth medium, which further supported the potential role of OsPAP26 in utilizing organic P in the rhizosphere. In summary, we concluded that OsPAP26 performs dual functions in plants: Pi remobilization from senescing to non-senescing leaves; and organic P utilization.

Analyses of Root-secreted Acid Phosphatase Activity in Arabidopsis

Induction and secretion of acid phosphatase (APase) is a universal adaptive response of higher plants to low-phosphate stress ( Tran et al., 2010 ). The intracellular APases are likely involved in the remobilization and recycling of phosphate (Pi) from intracellular Pi reserves, whereas the extracellular or secreted APases are believed to release Pi from organophosphate compounds in the rhizosphere. The phosphate starvation-induced secreted APases can be released into the rhizosphere or retained on root surfaces (root-associated APases). In this article, we describe the protocols for analyzing root-secreted APase activity in the model plant Arabidopsis thaliana (Arabidopsis). In Arabidopsis, the activity of both root-associated APases and APases that are released into the rhizosphere can be quantified based on their ability to cleave a synthesized substrate, para-nitrophenyl-phosphate (pNPP), which releases a yellow product, para-nitrophenol (pNP) ( Wang et al., 2011 and 2104). The root-associated APase activity can also be directly visualized by applying a chromogenic substrate, 5-bromo-4-chloro-3-indolyl-phosphate (BCIP), to the root surface ( Lloyd et al., 2001 ; Tomscha et al., 2004 ; Wang et al., 2011 and 2014) whereas the isozymes of APases that are released into rhizosphere can be profiled using an in-gel assay (Trull and Deikman, 1998; Tomscha et al., 2004 ; Wang et al., 2011 and 2014). The protocol for analysis of intracellular APase activity in Arabidopsis has been previously described (Vicki and William, 2013).

Influence of triethyl phosphate on phosphatase activity in shooting range soil: Isolation of a zinc-resistant bacterium with an acid phosphatase

Phosphatase-mediated hydrolysis of organic phosphate may be a viable means of stabilizing heavy metals via precipitation as a metal phosphate in bioremediation applications. We investigated the effect of triethyl phosphate (TEP) on soil microbial-phosphatase activity in a heavy-metal contaminated soil. Gaseous TEP has been used at subsurface sites for bioremediation of organic contaminants but not applied in heavy-metal contaminated areas. Little is known about how TEP affects microbial activity in soils and it is postulated that TEP can serve as a phosphate source in nutrient-poor groundwater and soil/sediments. Over a 3-week period, TEP amendment to microcosms containing heavy-metal contaminated soil resulted in increased activity of soil acid-phosphatase and repression of alkaline phosphatase, indicating a stimulatory effect on the microbial population. A soil-free enrichment of microorganisms adapted to heavy-metal and acidic conditions was derived from the TEP-amended soil microcosms using TEP as the sole phosphate source and the selected microbial consortium maintained a high acid-phosphatase activity with repression of alkaline phosphatase. Addition of 5mM zinc to soil-free microcosms had little effect on acid phosphatase but inhibited alkaline phosphatase. One bacterial member from the consortium, identified as Burkholderia cepacia sp., expressed an acid-phosphatase activity uninhibited by high concentrations of zinc and produced a soluble, indigo pigment under phosphate limitation. The pigment was produced in a phosphate-free medium and was not produced in the presence of TEP or phosphate ion, indicative of purple acid-phosphatase types that are pressed by bioavailable phosphate. These results demonstrate that TEP amendment was bioavailable and increased overall phosphatase activity in both soil and soil-free microcosms supporting the possibility of positive outcomes in bioremediation applications.

Isolation of Autolysosomes from Tobacco BY-2 Cells

Autolysosomes are organelles that sequester and degrade a portion of the cytoplasm during autophagy. Although autophagosomes are short lived compared to other organelles such as mitochondria, plastids, and peroxisomes, many autolysosomes accumulate in tobacco BY-2 cells cultured under sucrose starvation conditions in the presence of a cysteine protease inhibitor. We here describe our methodology for isolating autolysosomes from BY-2 cells by conventional cell fractionation using a Percoll gradient. The autolysosome fraction separates clearly from fractions containing mitochondria and peroxisomes. It contains acid phosphatase, vacuolar H+-ATPase, and protease activity. Electron micrographs show that the fraction contains partially degraded cytoplasm seen in autolysosomes before isolation although an autolysosome structure is only partially preserved.

Inhibition of cancer cell mitosis by reducing the availability of phosphate

The addition of phosphate groups is an essential requirement for the proper functioning of cyclin and cyclin dependent kinase which control various stages in the mitotic division of cancer cells. Thus limiting the availability of phosphate is likely to interfere with the metabolism of rapidly growing malignant cells. The human hormone glucagon and the anti metabolite mithramycin reduce serum phosphate by increasing phosphaturia and are both very effective in treating Paget's disease of bone, a precancerous condition. In this disorder large doses of glucagon given intravenously relieve bone pain and cause serum phosphate and alkaline phosphatase as well as urine hydroxyproline to fall, indicating a marked reduction in bone turnover. A constant iv infusion of glucagon was given to each of three patients all of whom had secondary malignant bone deposits. Two of the patients had primary prostate cancer and one had a squamous cell lung tumour. All three patients had relief of bone pain and a fall in serum alkaline phosphatase. Serum acid phosphatase also fell in the two patients with prostate cancer. It is proposed that the marked drop in serum phosphate due to glucagon causes intracellular phosphate to fall. This in turn disrupts the addition and removal of phosphate groups essential for the proper functioning of cyclin and cyclin dependent kinase. These two proteins control the transition from G1 to S (DNA synthesis phase) and G2 to M (mitotic phase) in the dividing cycle of malignant cells. Depriving a tumour of an essential ingredient used in phosphorylation reactions will disrupt its growth. It is also proposed that, by the same mechanism, glucagon induced hypophosphataemia renders malignant cells more sensitive to established chemotherapeutic agents and radiation waves. If this hypothesis proves to be correct, lowering intracellular phosphate may become an useful tool in cancer therapy. However extensive studies are necessary to determine whether mitosis in cancer cells can be advantageously disrupted by glucagon induced hypophosphataemia.