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Biomedical subjects

H Sandermann

Publications and source records attributed to H Sandermann.

At least 55 records · Page 3Linked to original sources
PubMed1993

Induction of lipid-protein mismatch by xenobiotics with general membrane targets.

Many membrane-active xenobiotics, such as organic solvents or general anesthetics, are without specific target sites. A common, but as yet ill-defined physical mechanism of action is usually assumed. Displacement of 'boundary' lipid activators from functional membrane proteins by the induction of lipid/protein mismatch is now established as a candidate common physical mechanism. Multiple binding site kinetics demonstrate that xenobiotics can be strongly inhibitory at realistic membrane concentrations of below 4 mol%. A general equation for inhibition is derived.

Binding Sites↗
PubMed1993

Molecular cloning, sequence analysis and elicitor-/ozone-induced accumulation of cinnamyl alcohol dehydrogenase from Norway spruce (Picea abies L.).

Cinnamyl alcohol dehydrogenase (CAD) is an enzyme involved in lignin biosynthesis. We have previously isolated pure CAD enzyme from Norway spruce (Picea abies L.) cell culture. Here we report on partial protein sequences of the 42 kDa CAD polypeptide. A cDNA encoding CAD was isolated from the spruce cell culture. The open reading frame of a full-length cDNA coded for a 357 amino acid polypeptide with a calculated M(r) of 38,777 Da. The identity of the deduced polypeptide was verified by comparison with amino acid sequences of tryptic peptides from the purified enzyme. Southern blot analysis showed the presence of only one gene for CAD. Sequence comparison with CAD from tobacco and with a N-terminal protein sequence from loblolly pine CAD showed an identity of 69.7% and 91.5%, respectively. Treatment of spruce cell cultures with elicitor, as well as of seedlings with ozone both markedly increased the CAD mRNA level.

Alcohol Oxidoreductases↗
PubMed1992

Ozone-induced changes of mRNA levels of beta-1,3-glucanase, chitinase and 'pathogenesis-related' protein 1b in tobacco plants.

Treatment of the ozone-sensitive tobacco cultivar Bel W3 with an ozone pulse (0.15 microliter/l, 5 h) markedly increased the mRNA level of basic beta-1,3-glucanase and to a lower degree that of basic chitinase. The increase of beta-1,3-glucanase mRNA level occurred within 1 h and showed a transient maximum. Seventeen hours after ozone treatment, the beta-1,3-glucanase mRNA level decreased to lower values. The increase of basic chitinase mRNA level was delayed and was less pronounced than that of beta-1,3-glucanase mRNA. Cultivar Bel B showed only a small increase of beta-1,3-glucanase mRNA level after the same ozone treatment, whereas its basic chitinase mRNA was more strongly induced. Prolonged ozone treatment for 2 days of tobacco Bel W3 led to a persistent level of beta-1,3-glucanase and basic chitinase mRNAs, as well as to an increase of acidic chitinase and 'pathogenesis-related' (PR) 1b mRNA levels. The results indicate that genes so far considered to code for PR proteins may also be involved in the plant response to oxidative stress.

Blotting, Northern↗
PubMed1992

Ozone is not mutagenic in the Tradescantia and tobacco mutagenicity assays.

Ozone fumigation of a double heterozygous chlorophyll mutant Nicotiana tabacum var. xanthi n.c. with concentrations up to 300 nl/l and of a heterozygous Tradescantia clone 4430 with concentrations up to 800 nl/l did not increase the frequency of somatic mutations above the spontaneous levels. However, ozone fumigation at these concentrations led to distinct physiological damage to plant tissues.

Dose-Response Relationship, Drug↗
PubMed1992

Plant metabolism of xenobiotics.

Metabolism of foreign chemicals (xenobiotics) by plants generally proceeds in three phases: transformation, conjugation and compartmentation. The participating enzymes have numerous similarities not only to the enzymes of normal secondary plant metabolism, but also to those of xenobiotic metabolism in mammalian liver. Plants may therefore be considered as a 'green liver', acting as an important global sink for environmental chemicals.

Animals↗
PubMed1992

Biochemical Plant Responses to Ozone : III. Activation of the Defense-Related Proteins beta-1,3-Glucanase and Chitinase in Tobacco Leaves.

A single pulse of O(3) (0.15 microliter per liter, 5 hours) induced beta-1,3-glucanase and chitinase activities in O(3)-sensitive and -tolerant tobacco (Nicotiana tabacum L.) cultivars. In the O(3)-sensitive cultivar Bel W3, the response was rapid (maximum after 5 to 10 hours) and was far more pronounced for beta-1,3-glucanase (40- to 75-fold) than for chitinase (4-fold). In the O(3)-tolerant cultivar Bel B, beta-1,3-glucanase was induced up to 30-fold and chitinase up to 3-fold under O(3) concentrations that did not lead to visible damage. Northern blot hybridization showed a marked increase in beta-1,3-glucanase mRNA in cultivar Bel W3 between 3 and 24 hours following O(3) treatment, a transient induction in cultivar Bel B, and no change in control plants. The induction of beta-1,3-glucanase and chitinase activities following O(3) treatment occurred within the leaf cells and was not found in the intercellular wash fluids. In addition, O(3) treatment increased the amount of the beta-1,3-glucan callose, which accumulated predominantly around the necrotic spots in cultivar Bel W3. The results demonstrate that near-ambient O(3) levels can induce pathogenesis-related proteins and may thereby alter the disposition of plants toward pathogen attack.

Journal Article↗
PubMed1991

Lipid-dependent membrane enzymes. Kinetic modelling of the activation of protein kinase C by phosphatidylserine.

A previously developed kinetic theory for lipid-dependent membrane enzymes (Sandermann, H. (1982) Eur. J. Biochem. 127, 123-128) is used to examine the activation of protein kinase C by phosphatidylserine. Hill-coefficients ranging up to 11 have been reported for activation in mixed micelles with Triton X-100. On the basis of this uniquely high degree of cooperativity, protein kinase C has been postulated to represent a new class of lipid-dependent membrane enzymes (Newton, A. and Koshland, D.E., Jr. (1989) J. Biol. Chem. 264, 14909-14915). In contrast, activation in the absence of Triton X-100 has led to Hill-coefficients of only less than or equal to 2.6. In order to resolve the apparent discrepancy, activation is now considered to involve binding of PS monomers to interacting sites on the enzyme, a non-activating PS trapping process also occurring in the presence of Triton X-100. Estimates for trapping are made for several sets of published data for micellar activation. The kinetic model developed here successfully fits each data set using a Hill-coefficient of only 3.0. An influence of Ca2+/ions or of a two-step mechanism of lipid-protein interaction are considered as possible molecular explanations. It is concluded (i) that lipid activation of protein kinase C may proceed without unique cooperativity and (ii) that ligand trapping could provide another means for 'threshold-type' kinetic regulation of membrane enzyme and receptor systems.

Calcium↗
PubMed1991

Isolation of functional RNA from plant tissues rich in phenolic compounds.

A method for the isolation of RNA from different tissues of trees (seedlings, saplings, and adult trees) is described. Using this procedure it is possible to remove large amounts of disturbing polyphenolic compounds from nucleic acids. The method involves an acetone treatment of the freeze-dried and powdered plant material, the use of high salt concentrations in the extraction buffer and an aqueous two-phase system. These steps were combined with the conventional phenol/chloroform extraction and CsCl centrifugation. The method has been successfully applied to the isolation and purification of RNA from pine (Pinus sylvestris L. and Pinus mugo Turr.), Norway spruce (Picea abies L.), and beech (Fagus sylvatica L.). The functional quality of RNA extracted by this procedure has been characterized by its uv spectrum, by agarose gel electrophoresis with ethidium bromide staining, Northern blot hybridization, and in vitro translation.

Acetone↗
PubMed1991

Plant biochemistry of xenobiotics: isolation and properties of soybean O- and N-glucosyl and O- and N-malonyltransferases for chlorinated phenols and anilines.

O-Glucosyltransferase (O-GT), O-malonyltransferase (O-MAT), N-glucosyltransferase (N-GT), and N-malonyltransferase (N-MAT) activities have been detected in cultured soybean cells, using pentachlorophenol and 3,4-dichloroaniline as xenobiotic standard substrates. The O-GT was purified approximately 1000-fold, and the N-MAT approximately 70-fold. There was an extensive copurification of O-GT and O-MAT. The following functional molecular weight values were obtained, 47 kDA (O-GT), 48 kDA (O-MAT) 43 kDa (N-GT), and 48 kDa (N-MAT). O-GT and N-MAT appeared to be monomeric polypeptides with isoelectric points of approximately 4.8 and approximately 6.1, respectively. The O-GT, N-GT, and N-MAT activities had marked substrate specificities for chlorinated aromatic xenobiotics and thus illustrate the existence of plant isoenzymes with specificity for xenobiotics.

Acyltransferases↗
PubMed1991

Biochemical plant responses to ozone : I. Differential induction of polyamine and ethylene biosynthesis in tobacco.

Polyamine metabolism was examined in tobacco (Nicotiana tabacum L.) exposed to a single ozone treatment (5 or 7 hours) and then postcultivated in pollutant-free air. The levels of free and conjugated putrescine were rapidly increased in the ozone-tolerant cultivar Bel B and remained high for 3 days. This accumulation was preceded by a transient rise of l-arginine decar-boxylase (ADC, EC 4.1.1.19) activity. The ozone-sensitive cultivar Bel W3 showed a rapid production of ethylene and high levels of 1-aminocyclopropane-1-carboxylic acid after 1 to 2 hours of exposure. Induction of putrescine levels and ADC activity was weak in this cultivar and was observed when necrotic lesions developed. Leaf injury occurred in both lines when the molar ratio of putrescine to 1-aminocyclopropane-1-carboxylic acid or ethylene fell short of a certain threshold value. Monocaffeoyl-putrescine, an effective scavenger for oxyradicals, was detected in the apo-plastic fluid of the leaves of cv Bel B and increased upon exposure to ozone. This extracellular localization could allow scavenging of ozone-derived oxyradicals at the first site of their generation. Induction of either polyamine or ethylene pathways may represent a control mechanism for inhibition or promotion of lesion formation and thereby contribute to the disposition of plants for ozone tolerance.

Journal Article↗
PubMed1991

Biochemical Plant Responses to Ozone : II. Induction of Stilbene Biosynthesis in Scots Pine (Pinus sylvestris L.) Seedlings.

Formation of the stilbenes pinosylvin and pinosylvin 3-methyl ether, as well as the activity of the biosynthetic enzyme stilbene synthase (pinosylvin-forming), were induced several hundred- to thousandfold in primary needles of 6-week-old pine (Pinus sylvestris L.) seedlings upon exposure to a single pulse of ozone of at least 0.15 microliters per liter. The seedlings required 4 hours of exposure as a minimum for the induction of stilbene biosynthesis when exposed to 0.2 microliters per liter ozone. Both stilbene synthase activity and stilbene accumulation increased with the duration of ozone treatment. The activity of phenylalanine ammonia-lyase and the activity of chalcone synthase, a key enzyme of the flavonoid pathway that uses the same substrates as stilbene synthase, were also stimulated about twofold by ozone. Stilbene biosynthesis appears to represent the first example of a dose-dependent biochemical response to ozone in a conifer species and may serve as a useful biomarker to study stress impacts on pine trees.

Journal Article↗
PubMed1990

Biochemical response of Norway spruce (Picea abies (L.) Karst.) towards 14-month exposure to ozone and acid mist: part I--Effects on polyphenol and monoterpene metabolism.

Three-year-old clonal Picea abies (L.) Karst. plants, grown either on a sandy (No. 1) or on a calcareous (No. 2) soil, were treated with ozone (100 microg m(-3) and peaks of up to 360 microg m(-3)) and acid mist (pH 3.0) over two vegetation periods. Needles of the current (1987) and previous (1986) year were analysed at the end of the experiment for biosynthetic enzymes and in vivo activity of the phenylpropanoid pathway, for products of polyphenol metabolism (clones 11 and 14), and for mono- and sesquiterpenes (clones 14 and 16). 1. Polyphenol metabolism. The activity of cinnamyl alcohol dehydrogenase, an enzyme of the lignin pathway, was increased by the treatment by up to 83% in the needles of both age classes. Chalcone synthase was measured in mature tree material for the first time. This enzyme, as well as phenylalanine ammonia-lyase activities and the content of catechin, astringin, isorhapontin, picein and p-hydroxyacetophenone, exhibited no significant treatment-dependent differences. However, soil and age-class dependent differences occurred. Pulse-labelling experiments with l[U-(14)C]phenylalanine and [2-(14)C]acetate were carried out at four different stages of shoot development and showed label incorporation into (+)-catechin and proanthocyanidins. There was no effect of the ozone and acid mist treatment. 2. Monoterpenes. The content of needle terpenes was generally diminished by the ozone and acid mist treatment. Other factors tested, such as clone, needle age and soil, exerted a highly significant influence on the content of most of the needle monoterpenes.

Journal Article↗
PubMed1990

Biochemical response of Norway spruce (Picea abies (L.) karst.) towards 14-month exposure to ozone and acid mist: part II--Effects on protein biosynthesis.

Four-year-old clonal Picea abies (L.) Karst. plants were treated with ozone (100 microm(-3) plus peaks of 130 to 360 microm(-3)) and acid mist (pH 3.0) during two vegetation periods. Pulse labelling experiments on shoots were performed with [(35)S]methionine in the second year of exposure. Extraction of soluble needle proteins in citric acid buffer of pH 2.8 revealed protein patterns on SDS polyacrylamide gels that differed from those of control needles fumigated with ambient levels of ozone (50 microg m(-3)) and mist of pH 5.6. New proteins of MW 16000 and 32000 were synthesized only in ozone-exposed needles and could not be detected in the controls.

Journal Article↗
PubMed1988

Lipid-dependent membrane enzymes. Purification to homogeneity and further characterization of diacylglycerol kinase from Escherichia coli.

1. Diacylglycerol kinase apoprotein was purified from membranes of Escherichia coli K12 by a six-step procedure that included HPLC. The proposed assignment of the enzyme to the dgkA gene [Lightner et al. (1983) J. Biol. Chem. 258, 10856-10861] could be supported by molecular mass determination (approximately 14 kDa), N-terminal sequencing (Met-Ala-Asn), cyanogen bromide fragmentation and amino acid analysis. As predicted, proline was absent. 2. The membrane-associated as well as the butan-1-ol-dissolved enzyme survived heating to 100 degrees C. 3. Alkylglycoside detergents were found to constitute an additional class of lipid activators. 4. The enzyme apoprotein in a non-activating substrate/detergent solution was capable of autocatalytic self-activation which was attributed to a novel feedback activation mechanism involving phosphatidic acid (diacylglycerol 3-phosphate).

Amino Acid Sequence↗
PubMed1988

Mutagenic activation of xenobiotics by plant enzymes.

Genetic evidence has indicated that plants can activate certain xenobiotics to mutagens, but biochemical evidence is as yet scarce. Nevertheless, plant microsomal enzymes and peroxidases have been shown to form reactive intermediates, the best studied examples being 2-aminofluorene, benzo[a]pyrene and pentachlorophenol. The latter two xenobiotics are converted to quinoid derivatives which are, in principle, able to redox cycle and generate active oxygen species. In analogy to results obtained in mammalian systems, covalent binding of reactive intermediates to DNA as well as fragmentation of DNA, are proposed as major mechanisms of action of mutagenic plant metabolites.

Animals↗
PubMed1987

[Pesticide residues in food plants: the role of plant metabolism].

The plant metabolism of pesticides typically leads to various classes of persistent "soluble" and "insoluble" conjugates whose structures and modes of formation and storage have been characterized only in recent years. Pesticide risk assessment should include studies on animal bioavailability and toxicological properties of the conjugates.

Animals↗