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PubMed1983

Host-Pathogen Interactions : XXII. A Galacturonic Acid Oligosaccharide from Plant Cell Walls Elicits Phytoalexins.

Elicitors of phytoalexin accumulation in soybean (Glycine max L. Merr., cv Wayne) cotyledons were released from soybean cell walls and from citrus pectin by partial acid hydrolysis. These two hydrolysates yielded nearly identical distributions of elicitor activity when fractionated on anion-exchange columns. Chromatography of the pectin elicitor on gel filtration and high-pressure anion-exchange columns did not further purify the elicitor. Elicitor activity of the preparation was lost by treatment with either endo-alpha-1,4-polygalacturonase or pectate lyase. Glycosyl residue compositions of the purified elicitors from cell walls and pectin were both found to be approximately 98% galacturonosyl residues. Linkage analysis of the pectin elicitor showed that most, if not all, of the galacturonosyl residues were alpha-1,4-linked. The high-mass molecular ions detected by fast atom bombardment-mass spectrometry of the most active elicitor fractions from cell walls and pectin both corresponded precisely to a molecule composed of 12 galacturonosyl residues. These results suggest that dodeca-alpha-1,4-d-galacturonide is the active elicitor, but the possibility remains that the active component could be a slightly modified oligogalacturonide present, but not detected, in the purified fractions.

Journal Article↗
PubMed1984

Role of Pectinesterase in pH-Dependent Interactions between Pea Cell Wall Polymers.

Extracts of etiolated pea (Pisum sativum L.) shoots converted soluble pectin from the seedlings to a trichloroacetic acid-insoluble form. This activity coincided with pectinesterase peaks separated from the extracts by gel filtration and ion exchange. The conversion of pectin to the trichloroacetic acid-insoluble form and pectinesterase exhibited identical responses to pH, with activity only above pH 6. The formation of trichloroacetic acid-insoluble pectin in pea cell walls and their extracts is due to de-esterification of the pectin by pectinesterase and not to binding between pectin and a protein, as reported in the literature.

Journal Article↗
PubMed1988

A survey of the pectic content of nonlignified monocot cell walls.

The primary cell walls of graminaceous monocots were known to have a low content of pectin compared to those of dicots, but it was uncertain how widespread this feature was within the monocots as a whole. Nonlignified cell walls were therefore prepared from 33 monocot species for determination of their pectin content. It was not possible to solubilize intact pectins quantitatively from the cell walls, and the pectin content was assessed from three criteria: the total uronic acid content; the content of alpha-(1,4')-D-galacturonan isolated by partial hydrolysis and characterized by electrophoresis and degradation by purified polygalacturonase; and the proportion of neutral residues in a representative pectic fraction solubilized by sequential beta-elimination and N,N,N'N'-cyclohexanediaminetetraacetic acid extraction. Low galacturonan contents were restricted to species from the Gramineae, Cyperaceae, Juncaceae, and Restionaceae. Other species related to these had intermediate galacturonan contents, and the remainder of the monocots examined had high galacturonan contents comparable with those of dicots. The other criteria of pectin content showed the same pattern.

Journal Article↗
PubMed1989

Purification and Characterization of Pectinmethylesterase from Ficus awkeotsang Makino Achenes.

Pectinmethylesterase from the pericarp of jelly fig (Ficus awkeotsang) achenes was extracted and purified to a specific activity of 289 micromole proton produced per minute per milligram protein. Pectinmethylesterase, a major protein with high specific activity in the crude extract, was monomeric with a molecular weight of 38,000. The enzyme preparation was stable in distilled water at 4 degrees C for at least 6 months, and at 60 degrees C for at least 10 minutes. This enzyme functioned optimally at pH 6.5 to 7.5 when the assay mixture contained no NaCl or at low NaCl concentration. The pH optimum shifted to lower pH as the NaCl concentration was increased. The K(m) value for pectin was 0.75 milligram per milliliter pectin, corresponding to a V(max) value of 310 micromoles per minute per milligram protein. Inhibition studies with antibodies indicated that jelly fig achene pectinmethylesterase and the two other pectinmethylesterases from orange and tomato were similar in their active site conformation; however, the surface determinants may be very different because no precipitation between anti-jelly fig pectinmethylesterase immune serum and the pectin methylesterase from orange and tomato could be observed in the double immunodiffusion analysis. Specific antisera raised against jelly fig achene pectinmethylesterase in a Western blot experiment also showed low similarity between jelly fig pectinmethylesterase with that from orange and tomato. This observation was also supported by the very low isoelectric point (pH 3.5) of jelly fig pectinmethylesterase, compared with high isoelectric points reported for most of the pectinmethylesterases. Amino acid composition and N-terminal sequence have been obtained. High homology of the N-terminal amino acid residues between jelly fig and tomato pectinmethylesterase (O Markovic, H Jornvall [1986] Eur J Biochem 158: 455-462) was observed. Pectinmethylesterase activity causes the release of protons from the deesterification of pectin such that a low pH environment is created, and this may be related to the cell growth. Pectinmethylesterase is not needed for jelly fig seed germination, however the gel formed from pectin and pectinmethylesterase may insure a water source for the germinating jelly fig seeds.

Journal Article↗
PubMed1998

Glomerular cytoarchitectures in chemosensory systems of arachnids.

In most animals the central pathways of olfactory systems are associated with glomerular neuropil and lack topographic mapping of sensory inputs. Among arthropods, the insect and crustacean olfactory (antennal) pathways are typical examples. Two orders of chelicerate arthropods, the scorpions and solpugids (Cl. Arachnida), present striking exceptions to this generalization. The major chemosensory organs of scorpions are the pectines, two ventral appendages that contact the substrate intermittently as the animal searches for food or mates. In solpugids chemosensory input is from the antennalized pedipalps and first leg pairs, and from ten fan-shaped malleoli extending ventrally to the substrate from the 4th leg pair. The pectinal and malleolar sensory systems have highly ordered arrangement of 10(5) to 10(6) primary chemoreceptors, with one (pectines) forming a two-dimensional array and the other (malleoli) assembled in a linear array. The spatial frequencies of these chemoreceptive inputs exceed 100/mm and 1000/mm, respectively, indicating a capacity for resolving structure of chemical deposits on substrates. Using several histological and axonal tracing techniques, the organization of pectinal and malleolar central projections has been resolved. The pectinal projection terminates posteriorly in the cephalothoracic mass and shows a high degree of topographic precision, perhaps to the level of individual receptors in the sensory field. This chemosensory 'map' is imposed on laminar cytoarchitecture posteriorly in the brain but merges anteriorly into glomerular substructures. The sensory projection from the malleoli shows less topographic order with fewer and larger glomeruli reminiscent of the insect olfactory system. These comparisons between arthropod taxa suggest that olfactory projections are, to varying degrees, typically glomerular but may evolve topographic and laminar organization when the stimulus field is of fixed form.

Animals↗
PubMed2001

Regulation of the expression of endopolygalacturonase gene PGU1 in Saccharomyces.

Previous work in our laboratory has shown that Saccharomyces bayanus strain SCPP is the only reported yeast expressing the three types of pectolytic enzymes: pectin esterases, pectin lyases and polygalacturonases. One of these enzymes, the endopolygalacturonase (endoPG), hydrolyses plant-specific polysaccharide pectin. The endoPG encoding gene (PGU1) is also present in Saccharomyces cerevisiae. It has been shown that this endoPG is required for the development of pseudohyphae. Using genomic DNA, the PGU1-1 and PGU1-2 promoters of these strains have been amplified and used to construct gene fusions with the beta-galactosidase gene. On the basis of beta-galactosidase measurements, we compared the expression of both promoters in different environmental conditions in order to identify their modulation. We have shown that the PGU1 gene is upregulated by the presence of the pectin and the product resulting from endopolygalacturonase activity. Moreover, expression of the PGU1 is also enhanced under respiratory and filament formation conditions.

Base Sequence↗
PubMed1993

Exocrine pancreatic secretions in pigs as influenced by the source of carbohydrate in the diet.

Four barrows, initial wt. 70 kg, fitted with permanent pancreatic cannulas according to the "Pouch Method", were used to investigate the effect of dietary inclusion of pectin on pancreatic secretions. The pigs were fed two corn starch-based diets, containing 16% crude protein from soybean meal, with 0 or 7.5% pectin. The pigs were fed twice daily, at 08:30 and 20:30, 900 g each meal. Pancreatic juice was collected continuously at 1-h intervals for a total of 24 h. The inclusion of pectin did not affect (p > .05) the flow of pancreatic juice and the total secretion of nitrogen, lipase, trypsin and chymotrypsin. However, there was a significant (p < .05) decrease in the secretion of alpha-amylase, which was actually a direct result of the replacement of starch by pectin.

Amylases↗
PubMed1994

New search for pectolytic yeasts.

A new screening method for pectin-depolymerizing microorganisms is described. The method is based on precipitation of non-hydrolyzed citrus pectin with hexadecyltrimethylammonium bromide in a medium solidified with a bacterial gelling gum. A substrate depolymerized by the secreted enzymes does not precipitate, and the positive strains thus show transparent areas around the colonies. The method was used to screen 300 yeast and yeast-like microorganisms belonging to 52 different genera. The secretion of pectin-depolymerizing enzymes occurred with different frequencies in 13 genera (69 positive strains of 207 tested), the lowest frequency being found in the genus Candida (13 positive out of 125 strains tested) and the highest frequency in the genera Aureobasidium (4 of 6) Cryptococcus (29 of 38), Geotrichum (4 of 9), Kluyveromyces (5 of 5), Rhodosporidium (2 of 2), Leucosporidium (2 of 2), Trichosporon (3 of 6) and Ustilago (2 of 2). Strains giving the highest number of harvested cells after growth on pectin in a liquid medium have been identified.

Cetrimonium↗
PubMed1991

Effect of delayed gastric emptying on fluoride absorption in the rat.

The rate and site of fluoride (F) absorption were compared in fasted 350 g male rats given 50 micrograms F (as NaF) in either water or a 7.5% pectin solution. Absorption was measured at intervals up to 2 h following gastric intubation. Gastric emptying was measured by inclusion of 14C-PEG in the F solution. The extent of gastric F absorption was derived from rates of gastric emptying (14C-PEG loss) and F loss. Pectin markedly slowed gastric emptying, but by 2 h, more than 90% of the solution had passed into the small intestine in both groups, and F absorption exceeded 90% in both groups. The rate of F absorption was initially much slower in the pectin group than in the group given F in water, and plasma F concentration increased more slowly and reached a lower maximum value. Absorption from the stomach was greater in the pectin group, but still accounted for only approx 25% of total gastrointestinal absorption. The reduced rate of F absorption and slower rise in plasma F concentration accompanying delayed gastric emptying indicate that passage of F into the small intestine is the major factor in rapid F absorption.

Animals↗
PubMed2000

Differential localization of arabinan and galactan side chains of rhamnogalacturonan 1 in cambial derivatives.

The development of pectin structural features during the differentiation of cambial derivatives was investigated in aspen (Populus tremula L. x P. tremuloides Michx.) using biochemical and immunocytochemical methods. Comparisons were also made between active and resting tissues. Active tissues, in particular cambial cells and phloem derivatives, were characterized by a high pectin content. Use of antibodies raised against arabinan side chains of rhamnogalacturonan 1 (LM6), as well as biochemical analysis, revealed an obvious decrease from the cortex to the differentiating xylem. Galactan side chains, detected with LM5 antibodies, were present mainly in the cambial zone and enlarging xylem cells. In contrast, they were totally absent from sieve-tube cell walls. Image analysis of LM5 immunogold labelling in the cambial zone showed a clustered distribution of galactan epitopes in the radial walls, a distribution which might result from the association of two different periodic processes, namely the exocytosis of galactan and wall expansion. Cessation of cambial activity was characterized by cell wall thickening accompanied by a sharp decrease in the relative amount of pectin and a lowering of the degree of methylesterification. The data provide evidence that the walls of phloem and xylem cells differ in their pectin composition even at a very early stage of commitment. These differences offer useful tools for identifying the initial cells among their immediate neighbours.

Cell Wall↗
PubMed1994

Dietary fiber values for various breads are higher using enzymatic analysis rather than detergent analysis.

OBJECTIVE: To compare the dietary fiber content of breads commonly eaten in Georgia, Michigan, Nevada, and Vermont. DESIGN: Dietary fiber content was determined according to neutral detergent fiber (NDF) plus pectin values and enzymatic gravimetric fiber values. White, whole-wheat, 100% stone-ground whole-wheat, cracked-wheat, and Roman Meal breads were analyzed for hemicellulose, cellulose, lignin, total NDF, pectin, and enzymatic gravimetric total fiber. STATISTICAL ANALYSES PERFORMED: Analysis of variance was used to determine significant F tests, and individual means were compared using Duncan's multiple range test. RESULTS: The 100% stone-ground whole-wheat bread had the most total fiber and fiber components followed by whole-wheat, Roman Meal, cracked-wheat, and white bread, except for pectin, of which Roman Meal had the most. The enzymatic gravimetric method of determining total fiber gave significantly (P < .0001) greater dietary fiber values than the values obtained by analyzing NDF plus pectin. These values ranged from 153% to 370% higher; however, there was a high degree of correlation (r = .95) between the methods. CONCLUSIONS: When recommending types of breads, dietitians should be aware of added ingredients that influence fiber values. When using published fiber values, dietitians should consider the technique used to quantify the fiber content.

Bread↗
PubMed2005

Non-covalent interaction between procyanidins and apple cell wall material. Part III: Study on model polysaccharides.

The adsorption of condensed tannins (procyanidins) of varying degrees of polymerisation and percentage of galloylation on solid polysaccharides substrates was quantified using the Langmuir isotherms formulation. Pectins and xyloglucans, which are soluble polysaccharides, were first cross-linked by, respectively, dibromopropane and epichlorohydrin to obtain insoluble covalent gels. Cellulose and starch, being insoluble in the buffer solution at room temperature, were used as bought. Apparent affinity constants obtained for the pure polysaccharides were as follows: pectin>>xyloglucan>starch>cellulose. The apparent affinity constants increased with the molecular weight of the procyanidins, except with cellulose. Higher affinities were obtained with pectin, a polysaccharide having the ability to develop a gel-like network, forming hydrophobic pockets able to encapsulate procyanidins. Filamentous and globular polysaccharides, like cellulose and xyloglucan, bound procyanidins weakly. Higher apparent saturation levels were obtained for cellulose and xyloglucans, the arrangement of which would favour cooperativity and stacking. Pectin had lower saturation levels probably due to a steric hindrance effect.

Absorption↗
PubMed2004

Physicochemical studies of pectin/poly-L-lysine gelation.

The effect of poly-L-lysine concentration and degree of polymerisation on the gelation of pectins differing in charge density and distribution was examined, through the determination of gel stiffness, swelling behaviour and the binding of poly-L-lysine to the gel network. Poly-L-lysine acts as a crosslinker of concentrated pectin solutions, with its effectiveness showing dependencies on pH and charge distribution on the pectin. Neutralisation of the anionic charge on the pectin with the polycationic peptide leads to gel opacity and eventually network collapse.

Biopolymers↗
PubMed2002

Expression profiling of pectinolytic genes from Aspergillus niger.

The expression of 26 pectinolytic genes from Aspergillus niger was studied in a wild type strain and a CreA derepressed strain, under 16 different growth conditions, to obtain an expression profile for each gene. These expression profiles were then submitted to cluster analysis to identify subsets of genes with similar expression profiles. With the exception of the feruloyl esterase encoding genes, all genes were expressed in the presence of D-galacturonic acid, polygalacturonate, and/or sugar beet pectin. Despite this general observation five distinct groups of genes were identified. The major group consisted of 12 genes of which the corresponding enzymes act on the pectin backbone and for which the expression, in general, is higher after 8 and 24 h of incubation, than after 2 or 4 h. Two other groups of genes encoding pectin main chain acting enzymes were detected. Two additional groups contained genes encoding L-arabinose and D-galactose releasing enzymes, and ferulic acid releasing enzymes, respectively. The genes encoding beta-galactosidase and the L-arabinose releasing enzymes were not only expressed in the presence of D-galacturonic acid, but also in the presence of L-arabinose, suggesting that they are under the control of two regulatory systems. Similarly, the rhamnogalacturonan acetylesterase encoding gene was not only expressed in the presence of D-galacturonic acid, polygalacturonate and sugar beet pectin, but also in the presence of L-rhamnose. The data presented provides indications for a general pectinolytic regulatory system responding to D-galacturonic acid or a metabolite derived from it. In addition, subsets of pectinolytic genes are expressed in response to the presence of L-arabinose, L-rhamnose or ferulic acid.

Aspergillus niger↗
PubMed2002

Texture of cooked potatoes (Solanum tuberosum). 3. Preheating and the consequences for the texture and cell wall chemistry.

Two potato cultivars representing extremes with regard to the texture of the cooked product were divided into subcategories based on size and dry matter (DM) content. The effects of the preheating temperature and time on both the instrumentally determined firmness and the sensory-perceived firmness were measured and compared. Increasing the preheating time at 60 degrees C followed by cooking resulted in greater force required to fracture the tissue, an increase in perceived firmness, and a less mashable product. A principal component analysis showed that with higher DM contents of the potato samples, preheating resulted in a larger force required to fracture the tissue and a firmer product. The changes in fracture force were not linearly related with the changes in perceived firmness. The effects of preheating on the pectin methylesterase (PME) activity, the enzyme assumed to be responsible for the firming effect upon preheating, showed that the activity of this enzyme remained rather constant during preheating at 60 degrees C for 1 h. Preheating at 78 degrees C for 10 min abolished virtually all PME activity. To obtain insight into the consequences of preheating and preheating followed by steam cooking on the yield and composition of the cell wall material (CWM) of potatoes, a cell wall isolation followed by a pectin fractionation study was performed. Attention was also paid to the consequences of the processing conditions applied on the chemical composition of the CWM and the sequentially extracted pectic fractions. Preheating resulted in an increase in yield of the CWM of cooked potatoes and, as a consequence, all of the sequentially extracted fractions, including the residue. Preheating did not have a pronounced effect on the composition of the pectin of the sequentially extracted fractions. This altogether strongly indicates that preheating causes a PME-based firming effect, resulting in an decrease in pectin degradation and, as a consequence, a larger yield of CWM. It seems reasonable to assume that this increase in amount of CWM results in a firmer texture. The contribution of starch-based degradation products to the texture after preheating can, however, not be excluded.

Carboxylic Ester Hydrolases↗
PubMed2004

Vacuum infusion of plant or fungal pectinmethylesterase and calcium affects the texture and structure of eggplant.

The effect of vacuum infusion on eggplant quality of a commercial fungal (Aspergillus niger) and citrus pectinmethylesterase (PME) with calcium chloride (4000 ppm) was investigated after processing and during storage. Firmness of infused eggplants using fungal or citrus PME was significantly increased compared to controls (fresh noninfused and water-infused control) after processing and during storage for 7 days at 4 degrees C. Activity of fungal PME-infused eggplant increased almost 32 times, whereas activity of eggplant infused with Marsh grapefruit PME increased 2-fold. Degree of esterification of pectin of eggplants infused with fungal or citrus PME decreased slightly. Cryo-SEM showed that samples treated with fungal PME/ CaCl2 displayed more integrity among cells as compared with water-infused control. The change of pectin in the cell wall was visualized using monoclonal antibodies JIM5 (low-esterified pectin) and JIM7 (high-esterified pectin). JIM5 showed more binding than JIM7 with the cell walls of eggplant tissues from fungal PME/ CaCl2 treatment.

Aspergillus niger↗
PubMed2006

Total antioxidant activity and fiber content of select Florida-grown tropical fruits.

Fourteen tropical fruits from south Florida (red guava, white guava, carambola, red pitaya (red dragon), white pitaya (white dragon), mamey sapote, sapodilla, lychee, longan, green mango, ripe mango, green papaya, and ripe papaya) were evaluated for antioxidant activity, total soluble phenolics (TSP), total ascorbic acid (TAA), total dietary fiber (TDF), and pectin. ORAC (oxygen radical absorbance capacity) and DPPH (1,1-diphenyl-2-picrylhydrazyl, radical scavenging activity) assays were used to determine antioxidant activity. The TSP, ORAC, and DPPH ranged from 205.4 to 2316.7 g gallic acid equiv/g puree, <0.1 to 16.7 micromol Trolox equiv/g puree, and 2.1 to 620.2 microg gallic acid equiv/g puree, respectively. The TAA, TDF, and pectin ranged from 7.5 to 188.8 mg/100 g, 0.9 to 7.2 g/100 g, and 0.20 to 1.04 g/100 g, respectively. The antioxidant activities, TSP, TAA, TDF, and pectin were influenced by cultivar (papaya, guava, and dragon fruit) and ripening stage (papaya and/or mango). Antioxidant activity showed high correlations with levels of TSP compounds (r = 0.96) but low correlations with levels of ascorbic acid (r = 0.35 and 0.23 for ORAC and DPPH data, respectively). The antioxidant activities evaluated by both ORAC and DPPH showed similar trends where red guava and carambola exhibited the highest and sapodilla and green papaya exhibited the lowest levels. Guava and mamey sapote exhibited the highest TDF and pectin levels. Many of the tropical fruits were shown to contain an abundance of hydrolyzable tannins, ellagic acid conjugates, and flavone glycosides. Preliminary descriptions are given of the phenols in red/white pitaya (dragonfruit), lychee, and mamey sapote, these fruit being thus far uncharacterized in the literature.

Antioxidants↗
PubMed1997

Application of a binary polymer system in drug release rate modulation. 1. Characterization of release mechanism.

A new binary polymer matrix tablet for oral administration was developed. The system will deliver drug at variable rates according to zero-order kinetics for total drug content and is manufactured by direct compression technology. Highly methoxylated pectin and hydroxypropyl methylcellulose (HPMC) at different ratios were used as major formulation components, and prednisolone was used as the drug model. The results indicate that by increasing pectin:HPMC ratios, release rates are increased, but zero-order kinetics prevail throughout the dissolution period (e.g., 3-22 h). Different pectin:HPMC ratios provide a range of viscosities that modulates drug release and results in rapid hydration/gelation in both axial and radial directions, as evidenced by photomicrographic pictures. This hydration-gelation contributes to the development of swelling/erosion boundaries and consequently to constant drug release. Combination of these particular polymers facilitates rapid formation of necessary boundaries (i.e., gel layer and solid core boundaries) to control overall mass transfer processes. The drug fraction released (Mt/M infinity), release kinetics, and mechanism of release were analyzed by applying the simple power law expression Mt/M infinity = kt(n), where k is a kinetic constant and the exponent n is indicative of the release mechanism. The calculated n values for pectin:HPMC ratios of 4:5, 3:6, and 2:7 were >0.95, which is indicative of a Case II transport mechanism (polymer relaxation/dissolution). The achievement of total zero-order kinetics is due to the predictable swelling/erosion and final polymer chain deaggregation and dissolution that is regulated by the gelling characteristics of polymers in the formulation.

Delayed-Action Preparations↗