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PubMed2000

Effect of pectinolytic enzymes on the theophylline release from pellets coated with water insoluble polymers containing pectin HM or calcium pectinate.

Theophylline pellets were coated with cellulosic (Aquacoat ECD 30, Surelease clear) or acrylic (Eudragit NE30D, RS30D) polymer aqueous dispersions, containing 10% (related to the insoluble polymer content) of pectin HM or calcium pectinate, using a Uni-Glatt fluidized-bed coating apparatus. When commercial pectinolytic enzymes were added to the dissolution media (0.05 M acetate - phosphate buffer, pH 6.0), the release of theophylline from the coated pellets was generally slower than that observed in the media without enzymes. The enzymatic slowing down of the drug release, depending on the type of the aqueous polymer dispersion used, is more important with mixed Eudragit NE/calcium pectinate coated pellets. The results obtained have been examined with regard to the validity of the approach based on the combination of pectins and the insoluble polymer aqueous dispersions intended for specific-delivery of drugs to the colon. The mechanism of the hydrophilic drug release from pellets coated with insoluble polymer aqueous dispersions containing an aqueous gel-forming polymer has been also discussed.

Absorption↗

PubMed2000

Pectin engineering: modification of potato pectin by in vivo expression of an endo-1,4-beta-D-galactanase.

Potato tuber pectin is rich in galactan (oligomer of beta-1,4-linked galactosyl residues). We have expressed a fungal endo-galactanase cDNA in potato under control of the granule bound starch synthase promoter to obtain expression of the enzyme in tubers during growth. The transgenic plants displayed no altered phenotype compared with the wild type. Fungal endo-galactanase activity was quantified in the transgenic tubers, and its expression was verified by Western blot analysis. The effect of the endo-galactanase activity on potato tuber pectin was studied by Fourier transform infrared microspectroscopy, immuno-gold labeling, and sugar analysis. All analyses revealed alterations in pectin composition. Monosaccharide composition of total cell walls and isolated rhamnogalacturonan I fragments showed a reduction in galactosyl content to 30% in the transformants compared with the wild type. Increased solubility of pectin from transgenic cell walls by endo-polygalacturonase/pectin methylesterase digestion points to other changes in wall architecture.

Genetic Engineering↗

PubMed1992

An Antisense Pectin Methylesterase Gene Alters Pectin Chemistry and Soluble Solids in Tomato Fruit.

Pectin methylesterase (PME, EC 3.1.11) demethoxylates pectins and is believed to be involved in degradation of pectic cell wall components by polygalacturonase in ripening tomato fruit. We have introduced antisense and sense chimeric PME genes into tomato to elucidate the role of PME in fruit development and ripening. Fruits from transgenic plants expressing high levels of antisense PME RNA showed <10% of wild-type PME enzyme activity and undetectable levels of PME protein and mRNA. Lower PME enzyme activity in fruits from transgenic plants was associated with an increased molecular weight and methylesterification of pectins and decreased levels of total and chelator soluble polyuronides in cell walls. The fruits of transgenic plants also contained higher levels of soluble solids than wild-type fruits. This trait was maintained in subsequent generations and segregated in normal Mendelian fashion with the antisense PME gene. These results indicate that reduction in PME enzyme activity in ripening tomato fruits had a marked influence on fruit pectin metabolism and increased the soluble solids content of fruits, but did not interfere with the ripening process.

Journal Article↗

PubMed1994

Detection of polygalacturonase, pectin-lyase and pectin-esterase activities in a Saccharomyces cerevisiae strain.

The catalytic capacity of several excreted pectinolytic enzymes obtained from various yeast strains was examined using in vivo and biochemical techniques. Of the 33 yeast strains studied, 30 were isolated from champagne wine during alcoholic fermentation. Only one yeast strain was found to excrete pectinolytic enzymes and was identified as Saccharomyces cerevisiae and designated SCPP. Pulsed-field gel electrophoresis and the polymerase chain reaction technique were used to characterize further this specific strain. Three types of pectinolytic enzymes were found to be excreted by SCPP: polygalacturonase, pectin-lyase and pectin-esterase. These enzymes allow pectin hydrolysis during cell growth.

Base Sequence↗

PubMed1990

Cloning and expression of a second Aspergillus niger pectin lyase gene (pelA): indications of a pectin lyase gene family in A. niger.

Using the previously cloned Aspergillus niger N756 pectin lyase D gene as a probe, the corresponding pelD gene has been isolated from a genomic library of the laboratory strain A. niger N400. This gene encodes PLD, previously described as PLI, which is one of the two major pectin lyases isolated from the commercial pectinase preparation Ultrazym. Heterologous hybridization of the A. niger N400 genomic library with the pelD gene led to the isolation of another five genes: pelA, B, C, E, and F. These genes differ in their hybridization patterns with probes containing either the entire pelD gene, or 5' or 3' parts thereof. By partial sequencing, and expression in an A. niger transformant containing multiple copies of the pelA gene, we show that this gene, which hybridizes strongest with the pelD gene, encodes the other major pectin lyase from Ultrazym, PLII.

Amino Acid Sequence↗

PubMed2001

Selective and sensitive detection of pectin lyase activity using a colorimetric test: application to the screening of microorganisms possessing pectin lyase activity.

Several methods have been described for the detection and quantification of polygalacturonase (PG) and pectin lyase (PL) activities. The most frequently used tests are the Nelson method using copper(II) and an arsenomolybdate reagent to detect PG activity, and the colorimetric method using thiobarbituric acid (TBA) to detect PL activity. We observed that none of these methods are suitable to differentiate between these two enzymatic activities. Therefore, we optimized the test conditions of the TBA method. As a result, the detection of the enzymatic beta-elimination (PL activity) became sensitive and selective. A basic pretreatment at 80 degrees C for 5 min of the solution which contains the pectin fragments of the PL activity furnished aldehydes which were condensed with TBA or its derivatives. After acidification of the medium, a pink fluorescent dye was detected spectrophotochemically (lambda = 550 nm). The interference of galacturonic acid or oligomers resulting from PG activity was completely eliminated. The most sensitive reagent was N-(pyridin-2-yl)-thiobarbituric acid. The application of this method with the new reagent was extended to the screening of microorganisms possessing the PL activity. The obtained results confirm that Aspergillus niger strain and a Saccharomyces cerevisiae SCPP strain possess this activity.

Aspergillus niger↗

PubMed2001

The effect of peptide-pectin interactions on the gelation behaviour of a plant cell wall pectin.

The effect of basic peptides on the gelation of a pectin from the cell wall of tomato was examined through the determination of gel stiffness, and swelling behaviour of the gel in water. Poly-L-lysine, poly-L-arginine, and a synthetic peptide, designed to mimic a sequence of basic amino acids found in a plant cell wall extensin, act as crosslinking agents. Circular dichroism studies on the interaction of synthetic extensin peptides with sodium polygalacturonate demonstrated that a conformational change was induced as a result of their complexation. In addition to their effect as crosslinking agents, the polycationic peptides reduced the swelling of the pectin network in water.

Amino Acid Sequence↗

PubMed2001

Involvement of pectin methyl-esterase during the ripening of grape berries: partial cDNA isolation, transcript expression and changes in the degree of methyl-esterification of cell wall pectins.

Grape berries (Vitis vinifera L., cv Ugni blanc) were harvested at 12 different weeks of development in 1996 and 1997. Ripening was induced at veraison, the crucial stage of berry softening, and was followed by a rapid accumulation of glucose and fructose and an increase of pH. Total RNAs, crude proteins and cell wall material were isolated from each developmental stage. A partial length cDNA (pme1, accession number AF159122, GenBank) encoding a pectin methyl-esterase (PME, EC 3.1.1.11) was cloned by RT-PCR with degenerate primers. Northern blots revealed that mRNAs coding for PME accumulate from one week before the onset of ripening until complete maturity, indicating that this transcript represents an early marker of veraison and could be involved in berry softening. However, PME activity was detected during all developmental stages. Total activity per berry increased, whereas "specific" activity, on a fresh weight basis, decreased during development. The amount of cell wall material (per berry and per g of berry) followed the same pattern as that of PME activity (total and "specific" respectively), indicating they were tightly correlated and that PME levels varied very little in the cell walls. Nevertheless, the degree of methyl-esterification of insoluble pectins decreased throughout the development from 68% in green stages to less than 20% for the ripe berries, and this observation is consistent with the induction of PME mRNAs during ripening. Relations between transcript expression, PME activity, the DE of insoluble pectic polysaccharides and their involvement in grape berry ripening are discussed.

Amino Acid Sequence↗

PubMedDate not supplied

Kinetics of the pectin methylesterase catalyzed de-esterification of pectin in frozen food model systems.

The pectin methylesterase (PME) catalyzed de-esterification of pectin was studied in four frozen food model systems based on sucrose, fructose, maltodextrin, and carboxymethylcellulose (CMC) in a temperature range from -24 to 20 degrees C, with the aim of elucidating the applicability of the theory of "food polymer science" on the kinetics. The rate substantially decreased around the glass transition temperature in the case of CMC, while very low rates were observed far above the glass transition temperature in the case of maltodextrin, fructose, and sucrose model systems. In general, the kinetics of this reaction was found to be influenced more by factors such as the characteristics of the component solutes, freeze concentration, the possible viscosity enhancement due to a particular combination of solutes, and the molecular size of the substrate molecule rather than the glass transition process. The Arrhenius equation described the temperature dependence of kinetics both in the liquid state of all the systems studied (r(2) > or = 0.97) and the glassy state of CMC (r(2) = 0.95). A clear break in the Arrhenius plot was observed as the temperature decreased to subfreezing temperatures. The Arrhenius equation could describe the kinetics reasonably well in the rubbery state for fructose and sucrose model systems (r(2) > 0.992). In the case of maltodextrin and CMC, the Arrhenius plots showed a slight curvature followed by a break at the glass transition temperature for CMC. The WLF equation with system-dependent coefficients better described the kinetics in the rubbery state of the CMC and part of the maltodextrin system. A linear relationship between the logarithm of the rate and T - Tg' described the kinetics in the sucrose as well as fructose model systems (r(2) = 0.9928 and 0.993, respectively).

Calorimetry↗

PubMedDate not supplied

Modeling the kinetics of the pectin methylesterase catalyzed de-esterfication of pectin in frozen systems.

The applicability of the William, Landel, and Ferry (WLF) equation with a modification to take into account the effect of melt-dilution and an empirical log-logistic equation were evaluated to model the kinetics of diffusion-controlled reactions in frozen systems. Kinetic data for the pectin methylesterase catalyzed hydrolysis of pectin in four model systems with different glass transition temperatures: sucrose, maltodextrin (DE = 16.5-19.5), carboxymethylcellulose (CMC) and fructose in a temperature range of -24 to 0 degrees C were used. The modified WLF equation was evaluated with a concentration-dependent glass transition temperature (T(g)) as well as the glass transition temperature of the maximally freeze-concentrated matrix (T(g)') as reference temperatures. The equation with temperature-dependent T(g) described the reaction kinetics reasonably well in all the model systems studied. However the kinetics was better described by a linear relationship between log(V(0)/V(0ref)) and (T - T(ref)) in all cases except CMC. The log-logistic equation also described the kinetics reasonably well. The effect of melt-dilution on reactant concentration was found to be minimal in all cases.

Carboxylic Ester Hydrolases↗

PubMed2002

Multivariate analysis of the influence of pectin, white syrup, and citric acid on aroma concentration in the headspace above pectin gels.

Pectin gels consist of polysaccharide networks surrounded by water. The gel networks can prevent release of aroma molecules from the gel to the gas phase above. In this study static headspace measurements were performed to correlate aroma concentration in the gas phase above pectin gels to different amounts of the gel ingredients. As a consequence, aroma concentration in the headspace in relation to gel texture, as characterized by rheology measurements, was also studied. Aroma concentration in the headspace above strong gels was low, due to entrapment of aroma molecules within the gel structure. Viscous solutions generally gave a high aroma concentration in the headspace, but owing to a complex matrix, this was lowered when large amounts of the gel ingredients were added. However, a high correlation between interaction terms and square terms of design variables and rheology parameters with aroma compounds indicated nonlinear and complex relationships.

Analysis of Variance↗

PubMed1994

Pectin Methylesterase Isoforms in Tomato (Lycopersicon esculentum) Tissues (Effects of Expression of a Pectin Methylesterase Antisense Gene).

We have identified two major groups of pectin methylesterase (PME, EC 3.1.1.11) isoforms in various tissues of tomatoes (Lycopersicon esculentum). These two groups exhibited differential immuno-cross-reactivity with polyclonal antibodies raised against tomato fruit PME or flax callus PME and differences in their accumulation patterns in tissues of wild-type and transgenic tomato plants expressing a PME antisense gene. The group I isoforms with isoelectric points (pls) of 8.2, 8.4, and 8.5 are specific to fruit tissue, where they are the major forms of PME activity. The group II PME isoforms, with pl values of 9 and above, are observed in both vegetative and fruit tissues. The group I isoforms cross-react with polyclonal antibodies raised to a PME isoform purified from fruit, whereas the group II isoforms cross-react with antibodies to a PME purified from flax callus. Expression of a fruit-specific PME anti-sense gene impairs accumulation of the group I PME isoforms, with no apparent effect on the accumulation of the group II PME isoforms. The absence of any noticeable effects on growth and development of transgenic plants suggests that the group I PME isoforms are not involved in plant growth and development and may play a role under special circumstances such as cell separation during fruit ripening.

Journal Article↗

PubMed1964