Inhibition Of Acid Phosphatase Activity Research Articles

Biochemical inhibition of acid phosphatase activity in two mountain spruce forest soils

The product inhibition of the 4-methylumbelliferyl phosphate (MUB-P) decay rate, a measure of potential acid phosphatase activity, has not been considered in most of the published kinetic studies. The aim of this study was to determine the type and strength of the product inhibition in order to better define reaction conditions at which the acid phosphatase activity assay produces unbiased results. The MUB-P decay rate was measured in the forest floor and topsoil organic horizons of two spruce forest catchments at different initial MUB-P and P-PO43− concentrations. The type and strength of the inhibition was analyzed by non-linear regression. We found that MUB-P decay was competitively inhibited by the P-PO43− but also by dissolved organic P. By using estimated kinetic parameters, we calculated an underestimation of potential acid phosphatase activity by up to ~ 20% at concentrations of added MUB-P as high as 300 µmol g−1 dry weight and an incubation time one hour due to background inorganic and organic P concentrations in range of units of µmol per gram of dry soil. We discuss approaches that can be used to minimize the underestimation and show that the previously defined recommendations might not be always sufficient to avoid the bias. Therefore, we recommend to analyze progress curves at a wide range of initial MUB-P concentrations using non-linear methods when the enzyme assay is optimized for a given soil. When changes in inorganic and/or organic P concentrations are expected, we further recommend measuring background inorganic and organic P concentrations.

CdSe/ZnS quantum dots coated with carboxy-PEG and modified with the terbium(III) complex of guanosine 5'-monophosphate as a fluorescent nanoprobe for ratiometric determination of arsenate via its inhibition of acid phosphatase activity.

A ratiometric fluorometric method is described for the determination of arsenate via its inhibitory effect on the activity of the enzyme acid phosphatase. A nanoprobe was designed that consists of CdSe/ZnS quantum dots (QDs) coated with the terbium(III) complex of guanosine monophosphate (Tb-GMP). The nanoprobe was synthesized from carboxylated QDs, Tb(III) and GMP via binding of Tb(III) by both the carboxy and the phosphate groups. The nanoprobe, under single-wavelength excitation (at 280nm), displays dual (red and green) emission, with peaks at around 652nm from the QDs, and at 547nm from the Tb-GMP coordination polymers. It is shown to be a viable nanoprobe for fluorometric determination of As(V) detection through it inhibitory action on the activity of acid phosphatase (ACP). The enzyme destroys the Tb-GMP structure via hydrolysis of GMP, and hence the fluorescence of the Tb-GMP complex is quenched. In contrast, the fluorescence of the CdSe/ZnS QDs remains inert to ACP. It therefore can serve as an internal reference signal. In the presence of arsenate (an analog of phosphate), the activity of ACP is inhibited due to competitive binding. Thus, hydrolysis of GMP is prevented. These findings were used to design a ratiometric fluorometric method for the quantification of As(V). The ratio of fluorescences at 547 and 652nm increases linearly in the 0.5 to 200ppb As(V) concentation range, and the limit of detection is 0.39ppb. Under a UV lamp, the probe shows distinguishable color from green to red on increasing the concentration of As(V). Graphical abstract Schematic illustration of CdSe/ZnS quantum dot coated with carboxy-PEG and modified with the terbium(III)-GMP complex as a fluorescent nanoprobe for ratiometric determination of arsenate via its inhibition of ACP activity.

Nanotoxicity of graphene oxide: Assessing the influence of oxidation debris in the presence of humic acid

This study sought to evaluate the toxicological effects of graphene oxide (GO) through tests with Danio rerio (zebrafish) embryos, considering the influence of the base washing treatment and the interaction with natural organic matter (i.e., humic acid, HA). A commercial sample of GO was refluxed with NaOH to remove oxidation debris (OD) byproducts, which resulted in a base washed GO sample (bw-GO). This process decreased the total oxygenated groups in bw-GO and its stability in water compared to GO. When tested in the presence of HA, both GO and bw-GO stabilities were enhanced in water. Although the embryo exposure showed no acute toxicity or malformation, the larvae exposed to GO showed a reduction in their overall length and acetylcholinesterase activity. In the presence of HA, GO also inhibited acid phosphatase activity. Our findings indicate a mitigation of material toxicity after OD removal. The difference in the biological effects may be related to the materials’ bioavailability and biophysicochemical interactions. This study reports for the first time the critical influence of OD on the GO material biological reactivity and HA interaction, providing new data for nanomaterial environmental risk assessment and sustainable nanotechnology.

Niobium(V) peroxo α-amino acid complexes: Synthesis, stability and kinetics of inhibition of acid phosphatase activity

The present work was undertaken with an objective to investigate some biologically relevant attributes of peroxoniobium (pNb) derivatives, using a set of heteroleptic pNb compounds containing biogenic species as co-ligands. New peroxoniobium complexes corresponding to the general formula, Na2[Nb(O2)3L] (L=alanine or valine) were synthesized and comprehensively characterized by elemental analysis, IR, Raman, 13C NMR, 1H NMR, AAS and UV–Vis spectral studies, as well as thermogravimetric analysis. The structures of the compounds have been studied by density functional theory (DFT) method and their stability in solution at physiological pH has been ascertained. These compounds, along with our previously reported arginine and nicotinate complexes, Na2[Nb(O2)3(arg)]·2H2O and Na2[Nb(O2)3(nic)(H2O)]·H2O, respectively were screened for their activities with two different types of enzymes viz., catalase and acid phosphatase (ACP). Employing wheat thylakoid ACP as the model enzyme, it has been demonstrated for the first time that peroxoniobium derivatives serve as active inhibitors of phosphatase (IC50 values 2–9μM). Enzyme kinetics data revealed that compounds exert mixed type of inhibition on ACP activity (Kii>Ki). Each of the tested pNb species exhibited significant resistance to degradation under the effect of catalase vis-a-vis the native substrate of the enzyme, H2O2.

A miniaturized optical biosensor for the detection of Hg2+ based on acid phosphatase inhibition

In the present study, a simple low cost and portable optical biosensor has been fabricated for the detection of Hg2+ based on inhibition of acid phosphatase activity. Poly-dimethoxysiloxane (PDMS) sensor chip module containing reaction and detection wells was fabricated. Acid phosphatase from the seeds of Macrotyloma uniflorum was immobilized at the bottom of reaction well to carry out the enzymatic reaction using p-nitrophenyl phosphate as a synthetic substrate. The detection was based on the measurement of transmitted light intensity through the yellow coloured solution of p-nitrophenol (λ405) liberated as a result of enzymatic reaction and was measured in terms of volts. The optical system was successfully employed for the detection of Hg2+ based on inhibition of enzyme activity. Response of the sensor was found to be linear in the range of 0.01–10mM. The biosensor was stable up to 20days of storage at 4°C without any appreciable loss in activity.

Effects of different concentrations of metal ions on degradation of adenosine triphosphate in common carp (Cyprinus carpio) fillets stored at 4 °C: An in vivo study

The impact of different concentrations of Na+, K+, Ca2+, Mg2+, Fe2+, and Zn2+ on the degradation of adenosine triphosphate (ATP) and the influence of these ions on the activity of adenosine monophosphate deaminase (AMP-deaminase) and acid phosphatase (ACP) in common carp fillets (in vivo) during 4°C storage was examined. The content of ATP, inosine monophosphate (IMP), and hypoxanthine (Hx), and the activity of AMP-deaminase and ACP were determined. Results indicated that the effects of different concentrations of six kinds of metal ions on AMP-deaminase and ACP were not the same. Na+, K+, Fe2+, and Zn2+ enhanced AMP-deaminase activity, which led to the rapid degradation of ATP and to the generation of a large quantity of IMP within a short time. Ca2+ and Mg2+ delayed the change in AMP-deaminase and ACP activity in carp and caused a further delay in the degradation of ATP. Fe2+ and Zn2+ inhibited ACP activity, which reduced the decomposition of IMP and the formation of Hx.

Fish exposure to nano-TiO2 under different experimental conditions: Methodological aspects for nanoecotoxicology investigations

The ecotoxicology of nano-TiO2 has been extensively studied in recent years; however, few toxicological investigations have considered the photocatalytic properties of the substance, which can increase its toxicity to aquatic biota. The aim of this work was to evaluate the effects on fish exposed to different nano-TiO2 concentrations and illumination conditions. The interaction of these variables was investigated by observing the survival of the organisms, together with biomarkers of biochemical and genetic alterations. Fish (Piaractus mesopotamicus) were exposed for 96h to 0, 1, 10, and 100mg/L of nano-TiO2, under visible light, and visible light with ultraviolet (UV) light (22.47J/cm2/h). The following biomarkers of oxidative stress were monitored in the liver: concentrations of lipid hydroperoxide and carbonylated protein, and specific activities of superoxide dismutase, catalase, and glutathione S-transferase. Other biomarkers of physiological function were also studied: the specific activities of acid phosphatase and Na,K-ATPase were analyzed in the liver and brain, respectively, and the concentration of metallothionein was measured in the gills. In addition, micronucleus and comet assays were performed with blood as genotoxic biomarkers. Nano-TiO2 caused no mortality under any of the conditions tested, but induced sublethal effects that were influenced by illumination condition. Under both illumination conditions tested, exposure to 100mg/L showed an inhibition of acid phosphatase activity. Under visible light, there was an increase in metallothionein level in fish exposed to 1mg/L of nano-TiO2. Under UV light, protein carbonylation was reduced in groups exposed to 1 and 10mg/L, while nucleus alterations in erythrocytes were higher in fish exposed to 10mg/L. As well as improving the understanding of nano-TiO2 toxicity, the findings demonstrated the importance of considering the experimental conditions in nanoecotoxicological tests. This work provides information for the development of protocols to study substances whose toxicity is affected by illumination conditions.

The actions of some non-steroidal drugs on lysosomes.

Abstract Several non-steroidal acidic anti-inflammatory drugs had a lytic action on lysosomes at high concentrations but no apparant action at lower concentrations. The drugs also inhibited acid phosphatase activity but only at high concentrations. High concentrations of drugs accelerated the thermal denaturation of albumin solutions but partially protected the albumin against denaturation at lower concentrations. The possibility that the denaturing action of drugs on proteins at high concentrations is related to lysosomal damage and that this damage may be associated with ulceration in vivo is discussed. Salicylate was found to inhibit the stabilizing action of cortisol on lysosomes.

Changes in phosphate content and phosphatase activities in rice seedlings exposed to arsenite

The effect of arsenite (As2O3) in situ on the level of the phosphate pool and activities of phosphohydrolytic enzymes was examined in rice (Oryza sativa L.) seedlings grown for 5-20 d in sand cultures. The effects were manifested via a decline in phosphate content and inhibition of the activities of key phosphatases. Application of 50 µM As2O3 in situ resulted in 34 to 77% inhibition of acid phosphatase activity in roots and about 38 to 50% inhibition of activity in shoots of 15-20-d-old seedlings. Similarly, alkaline phosphatase activity was inhibited in shoots under in situ As (III) toxicity. Varietal as well as organ specific differences were observed in the response of inorganic pyrophosphatase activity to in situ As (III) treatment. A moderately toxic in situ As2O3 level of 25 µM as well as a highly toxic level of 50 µM inhibited mitochondrial-ATPase activity whereas 25 µM As (III) stimulated the chloroplastic isoform of ATPase but at a higher level (50 µM) As (III) was inhibitory. The results suggest that exposure of rice plants to arsenite leads to lowering of the phosphate pool and alteration in the activities of key phosphohydrolytic enzymes which might contribute to metabolic perturbations and decreased growth of rice plants in an As (III) polluted environment.

Resistance of Surface Phosphohydrolases of Barley Root Cells to Nickel Salts Is One of Factors of Plant Adaptation to Excessive Nickel in the Environment

We studied the effect of nickel ions on the activity of ecto-phosphohydrolases (acid phosphatase and Ca-stimulated nucleotidase) from root surface of etiolated barley seedlings as well as from root microsomal fraction. The presence of nickel nitrate (25 microM) proved to stop root growth and insignificantly (on average by 20%) decreased specific hydrolytic activity of both enzymes determined on root surface as well as in the root microsomal fraction. At the same time, direct addition of nickel to the incubation mixture when measuring the substrate hydrolysis demonstrated high resistance of the microsomal fraction enzymes to the salts. A significant decrease in Ca-stimulated nucleotidase activity was observed only for nickel nitrate concentrations above 100 microM, reaching 50-60% for 3 mM Ni(NO3)2. The presence of an activator ion as well as extended duration of the microsomal fraction pretreatment with nickel nitrate (2.5 h) did not increase its effect on the enzyme activity. The pattern of nickel effect on acid phosphatase activity depended on the presence of magnesium ions in the mixture but did not change after extended duration of the microsomal fraction pretreatment (3 h). Inhibition of acid phosphatase activity in the presence of magnesium was observed only for nickel nitrate concentrations above 500 microM being no more than 20% for 3 mM Ni(NO3)2. Hence, the hydrolytic enzymes of the apoplast of plant root cells have different tolerance to to nickel salts. We propose that an insignificant decrease in specific activity of surface hydrolases of plant roots grown on a medium containing nickel salts in concentrations inhibiting growth processes (25 microM) is not related to direct effect of Ni on the apoplastic enzymes. The significance of hydrolytic enzyme resistance in plant adaptation to high nickel content in the soil is discussed.

Protein productivity of cell-free translation was improved by removing phosphatase from wheat germ extract with immunoprecipitation

The biochemical energy charge, ([ATP] + [ADP]/2)/([ATP] + [ADP] + [AMP]), is necessary to be kept at a high level close to 1.0 for protein synthesis in a cell-free translation system. Aiming at improvement of protein productivity of wheat germ extract (WGE) cell-free translation system, the authors developed a method of maintaining the energy charge at the high level by removing acid phosphatase activity of hydrolyzing ATP from the system. About 3 unit/ml activity of acid phosphatase (ACP) was detected in WGE. The detected activity of ACP accounted for 90% of ATP consumption in WGE cell-free translation system. Immunoprecipitation of ACP with ACP-specific antiserum reduced ACP activity in WGE by 60%. As the result, the energy charge in the translation system was kept above 0.97 for 150 min when the antiserum-treated WGE was used, while it was kept so for only 40 min when the untreated WGE was used. The protein productivity of the translation system increased 5-fold by the immunoprecipitation of ACP. Affinity separation of ACP with cellulose phosphate, or inhibition of ACP activity with inhibitors such as molybdate and vanadate reduced ACP activity in the translation system. However, these non-biological methods resulted in decrease rather than increase in protein productivity.

PH-altered interaction of aluminium and fluoride on nutrient uptake, photosynthesis and other variables of Chlorella vulgaris

This study presents information on the pH-induced toxicity of AlCl 3, AlF 3, NaF and AlCl 3+NaF on growth, nutrient uptake, photosynthesis, photosynthetic electron transport, enzymes of nitrogen and phosphorus metabolism and ATPase activity of Chlorella vulgaris. Both PS I and PS II were severely inhibited by the combination of AlCl 3+NaF followed by AlF 3, AlCl 3 and NaF. Inhibition of acid phosphatase activity was more pronounced than alkaline phosphatase. In general, toxicity of all the test chemicals increased with a downshift in pH. The interaction of AlCl 3 and NaF produced additive effect at pH 6.8, and synergistic at pH 6.0 and 4.5. The combination of AlCl 3+NaF did not produce significant difference in the activity of Mg 2+ and Ca 2+-ATPase in the medium supplemented with 60 and 100 μM PO 4 3− at pH 6.8. Compared to 60 μM PO 4 3−, the test organism grown in 100 μM PO 4 3− containing medium depicted significant increase in Mg 2+ and Ca 2+-ATPase activity at pH 6.0 and 4.5. Infra-red spectra revealed the formation of AlF 4 − at pH 6.0 and 4.5 in AlCl 3+NaF supplemented medium as well as in the algal cells. Aluminium uptake from the medium containing AlCl 3 decreased in the presence of PO 4 3−. This study suggests that phosphate restricts the entry of Al into the cell, while fluoride promotes it. AlF 4 − toxicity could be due to its interference with phosphate binding site of ATPase thereby arresting the release of energy.

Fluorescent cytochemistry of acid phosphatase and demonstration of fluid-phase endocytosis using an azo dye method.

The aim of this work was the development of a fluorescent microscopy technique to visualize acid phosphatase activity in living and pre-fixed cells. We have shown that a coupling azo dye method, using naphthol AS-MX phosphate (NP) as substrate and fast red TR (FR) as a diazonium salt coupling agent, gives rise to a fluorescent azo dye reaction product which permits a highly sensitive demonstration of lysosomal acid phosphatase in both living and pre-fixed monolayer cell cultures. The granular staining is prevented by inhibition of acid phosphatase activity using fluoride and/or orthovanadate in both living and pre-fixed preparations. Lysosomal staining in living cells is also abolished by inhibition of fluid-phase endocytosis using low temperatures or inhibition of oxidative phosphorylation. It was shown that whilst NP entered living cells by passive diffusion, occurrence of FR in lysosomes resulted from fluid-phase endocytosis. Spectroscopic analysis of the emission and absorption features of FR, NP, naphthol AS-MX (N), and the N-FR azo dye reaction product in solution corroborated our microscopic results. The differing uptake mechanisms, and the occurrence of lysosomally localized azo dye, were also in keeping with the predictions of quantitative structure-activity relationship models of this system.

Ultrastructural and histochemical study of β‐tricalcium phosphate resorbing cells in periodontium of dogs

beta-TCP was implanted in surgically prepared alveolar bone defects on the mesial side of the upper canine. The dogs that we used were sacrificed after 5 weeks, fixed by perfusion, and the beta-TCP resorbing cells were examined ultrastructurally and histochemically, with the following results: (1) beta-TCP was resorbed by macrophages and multinucleated giant cells. (2) Mitochondria, vacuoles and Golgi apparatus were abundant in beta-TCP-resorbing multinucleated giant cells that possessed neither ruffled borders nor clear zones. (3) The addition of tartric acid inhibited acid phosphatase activity in the cytoplasm of the multinucleated giant cells and macrophages.

Phosphatase activity in corn and soybean roots: Conditions for assay and effects of metals

Studies with sterile root materials showed that the optimum pH values of phosphatase activity in three varieties of each of corn (Zea mays L.) and soybean (Glycine max. L.) were 4 and 5, respectively. The activity on either side of the optimum pH fell sharply, and there was no activity at pH 9. Thus, these roots contain acid but no alkaline phosphatase activity. Acid phosphatase activity was not uniformly distributed in roots and root hairs. Studies with 20 metals showed that their effectiveness in inhibiting acid phosphatase activity of roots varied with the type of plant used. When the metals were compared at 250 μM (1.25 μmole. 5 mg−1 of homogenized roots), the inhibition of acid phosphatase of corn and soybean roots showed that Ag(I), Fe(III), Se(IV), V(IV), As(V) and Mo(VI) were the most effective inhibitors of this enzyme in corn roots, with percentage inhibition ≥30%. In addition to these metals, Sn(II), Hg(II), and W(VI) inhibited acid phosphatase in soybean roots by >30%. Other metals and one non-metallic element that inhibited acid phosphatase activity in corn and soybean roots were: Cu(I), Cu(II), Cd(II), Ni(II), Fe(II), Pb(II), Ba(II), Co(II), Mn(II), Zn(II), B(III), As(III), Cr(III), and Al(III); their degrees of effectiveness varied with type of roots used. Generally, the inhibitory effect of the metals was much less when their concentration was decreased by 10-fold. In addition to the effect of these elements, phosphate ion inhibited acid phosphatase activity of corn and soybean roots. Related anions such as NO 2 − , NO 3 − , Cl−, and SO 4 2− were not inhibitory.

The function of metabolism in phosphorus accumulation in plant roots and its transport over long distances

The values of influx (Ji) and efflux (Jo) of phosphates through intact maize roots (primary, seed roots) have confirmed the dependence of the P concentration in nutrient medium on the activity and efficiency of transport mechanism with respect to the accumulation of phosphates (J) by roots. The phosphate accumulation is about 97–99 % of the total uptake. If the P concentration is < 1 mM the efflux is negligible, and Ji <=g Jo. In contrast, if the P concentration is τ 1 mM, the proportion of efflux significantly increases, up to 45 % of the whole influx. The approximation to the conditions of equilibrium of phosphate flows ( Ji = Jo) depends on the P concentration in root cells, the accumulation of phosphates being determined by the relation Ji τ Jo. In the roots growing in P-containing medium the values of efflux are much higher than in the roots lacking P. The positive effect of Ca2+ ions on the accumulation of phosphates is caused by the decreased proportion of efflux. The factors instigating the integrity or non-integrity of the cell structure (Ca2+, SDS, EDTA, Sorbitol,etc.) and thus its effectiveness determine the accumulation of phosphates by roots. Analogously, the factors stimulating the ability of accepted phosphate to be metabolized, and their use in the form of organic compounds decrease the proportion of efflux; these activities are shown in the increased efficiency of the phosphate uptake. The presented results show the importance of the integrity of the cell structure, the functioning of membranes and of metabolism efficiency for the accumulation of phosphates by plant roots. The main form of phosphorus transport in xylem exudate is inorganic phosphorus. Its share is from 79 to 82 % of the total amount of transported P. The utilization of P in the roots in the form of organic, slowly motabolizable P compounds (mannose-6-phosphate) and inhibition of acid phosphatase activity effectively restrains P transport over long distances. The correlation of P transport from roots into shoots with phosphatase activity was established (correlation coefficient is 0.74++). It can be summarized that long-distance P tran sport is a function of dephosphorylating reactions.

Anti-androgens do not alter androgen-dependent characteristics of acid phosphatase in the rat ventral prostate

When administered to intact adult male rats, cyproterone acetate (10 mg/day), flutamide (15 mg/day), or Compound I (1 mg/day) caused a significant decrease in the organ weight to body weight ratios, with a concomitant rise in the specific activity of prostatic acid phosphatase. These compounds do not affect two other markers of androgen activity in the prostate. Neither the percentage inhibition of acid phosphatase activity by tartrate nor the appearance of the secretory band of acid phosphatase on polyacrylamide gels was altered by the administration of anti-androgens. When administered to castrated rats given doses of 5α-dihydrotestosterone (250–750 μg/day), flutamide (15 mg/day) was unable to alter the percentage inhibition of acid phosphatase activity by tartrate, or the pattern of activity on polyacrylamide gels. These results suggest that these anti-androgens affect only some of the androgen-dependent functions of the prostate.

An enzyme histochemical study of human salivary duct calculi.

An investigation was undertaken to study the distribution of enzymes associated with submandibular gland salivary calculi. Ten calculi were freeze-sectioned and incubated for acid and alkaline phosphatases and for lactate, succinate and maleate dehydrogenases. All calculi were partly covered by a 50-210 micrometers wide zone of organic material consisting of connective tissue and metaplastic squamous epithelium facing the mineralized calculus, or of a structureless substance attached to the mineralized calculus. The epithelium showed an intense staining reaction for acid phosphatase and lactate dehydrogenase and a moderate reaction for succinate dehydrogenase throughout all levels of the epithelium. The structureless peripheral zone exhibited a moderate activity of acid phosphatase and succinate dehydrogenase located to an area close to the mineralized matrix. Also alkaline phosphatase and lactate dehydrogenase were found in a special pattern in the structureless zone. Sodium fluoride and sodium vanadate added to the incubation medium inhibited acid phosphatase activity whereas cupric chloride only lowered the staining reaction. Enzyme activity was found only within the peripheral zone of organic material with one exception. The results suggest that the calcification process of salivary calculi is not a passive calcification of necrotic material or mucin but rather an active process promoted by enzymes in the surrounding organic substances.

Synthesis of poly(a) polymerase from conserved messenger RNA in germinating excised embryos of wheat

A 3.5–6.0-fold stimulation of poly(A) polymerase activity was observed in excised wheat embryos germinated for 48 hr. Addition of primer RNA to the enzyme assay mixture was necessary for the incorporation of [ 3H]AMP into the acid-precipitable polyadenylate product. Administration of six amino acid analogues (1 mM each) or cycloheximide (10 μg/ml) to the germinating embryos resulted in 77–82 % inhibition of poly(A) polymerase activity. The inhibitory response, elicited by the analogues, was substantially counteracted by the simultaneous addition of the corresponding six amino acids (2 mM each). This indicated that de novo protein synthesis was necessary for the enhancement of poly(A) polymerase activity. Cordycepin, a potent inhibitor of transcription, failed to block poly(A) polymerase activity; instead, the drug invariably brought about a significant stimulation ( ca 1.7–4.0-fold of the enzyme activity. Cordycepin, however, inhibited acid phosphatase activity by 77% in germinating wheat embryos. Actinomycin D also failed to inhibit poly(A) polymerase activity in germinating wheat embryos. The lack of inhibition of poly(A) polymerase by transcriptional inhibitors during early germination suggested that the enzyme was translated from its conserved mRNA, already stored in the dry wheat embryos.

Sensitivity to SO2 of Various Metabolic Processes in an Epiphytic Lichen, Evernia mesomorpha

Summary In the epiphytic lichen Evernia mesomorpha NYL., metabolic proeesses such as photosynthetic CO 2 -fixation and protein and lipid biosyntheses were found to be very sensitive to SO 2 . Exposure of lichens to 0.1 ppm of gaseous SO 2 for increasing durations produced a progressive reduction in these processes. Protein biosynthesis appeared to be the process most sensitive to SO 2 . Fumigation of lichen tissues at 0.34 ppm of SO 2 for increasing durations caused an increased phytotoxic effect on all three metabolic processes. Such fumigations also inhibited acid phosphatase activity and caused an increase in the sulphur content of the tissues. During an SO 2 -free period after the fumigations, these metabolic processes recovered partially or completely in liehens exposed to 0.1 ppm SO 2 but showed little or no recovery in lichens exposed to 0.34 ppm SO 2 .