ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Regulation of α-galactosidase activity and the hydrolysis of galactomannan in the endosperm of the fenugreek (Trigonella foenum-graecum L.) seed (1985)
    Springer
    Planta 166 (1985), S. 271-275 
    Details
    ISSN: 1432-2048
    Keywords: Endosperm ; Galactomannan ; α-Galactosidase ; Germination (seed) ; Seed germination ; Trigonella
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When endosperms were isolated from fenugreek seeds 5 h after sowing and incubated in a small volume of water, the development of α-galactosidase activity and the breakdown of the galactomannan storage polysaccharide were both inhibited relative to control endosperms incubated in larger volumes. The inhibition could be relieved by pre-washing the endosperms, and reimposed by the wash-liquors. If the endosperms were isolated 24 h after sowing, no inhibition was observed. Removal of the embryonic axis from germinating fenugreek seeds and from germinated seedlings also inhibited the development of α-galactosidase activity and galactomannan breakdown in the endosperms; the inhibition was more pronounced the earlier the axis was removed. Axis excision 5 h after sowing caused a delay in the onset of galactomannan breakdown and of the appearance of α-galactosidase activity in the endosperms. It also led to a decrease in the rates of galactomannan breakdown and α-galactosidase production. Axis excision 24 h after sowing caused only a slowing of the rates of galactomannan breakdown and α-galactosidase increase. The inhibition caused by axis removal at 5 h could be relieved partially by gibberellin (10-4 M), benzyladenine (10-5 M), mixtures of these and by the herbicide SAN 9789 [4-chloro-5-(methylamine)-2-(α,α,α-trifluoro-m-tolyl)-3-(2H)-pyridazinone]. These substances had no effect on the inhibition caused by axis-removal at 24 h. Excision of the cotyledons at 5 h-leaving the separated axis and the endosperm-also caused inhibition of galactomannan breakdown and α-galactosidase development. The results are consistent with the presence in the fenugreek seed endosperm of diffusible inhibitors of galactomannan mobilisation which are removed or inactivated during normal germination and early seedling development. They are also consistent with a role for the seedling axis in the control of galactomannan breakdown in the endosperm. Initially the axis appears to have a regulatory function (via gibberellins and/or cytokinins?) in determining the onset of α-galactosidase production in the endosperm. Thereafter its continued presence is necessary to ensure maximal rates of α-galactosidase production and galactomannan hydrolysis. The role of the axis may be initially to counteract the endogenous inhibitors in the endosperm and then to act as a sink for the galactomannan breakdown products released in the endosperm and taken up by the cotyledons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397359
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Control of mannose/galactose ratio during galactomannan formation in developing legume seeds (1992)
    Springer
    Planta 187 (1992), S. 67-74 
    Details
    ISSN: 1432-2048
    Keywords: Alpha galactosidase ; Cell wall storage polysaccharide ; Cyamopsis ; Galactomannan (biosynthesis) ; Senna ; Trigonella
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Galactomannan deposition was investigated in developing endosperms of three leguminous species representative of taxonomic groups which have galactomannans with high, medium and low galactose content. These were fenugreek (Trigonella foenum-graecum L.; mannose/galactose (Man/Gal) = 1.1), guar (Cyamopsis tetragonoloba (L.) Taub.; Man/Gal = 1.6) and Senna occidentalis (L.) Link. (Man/Gal = 3.3), respectively. Endosperms were analysed at different stages of seed development for galactomannan content and the levels, in cell-free extracts, of a mannosyltransferase and a galactosyltransferase which have been shown to catalyse galactomannan biosynthesis in vitro (M. Edwards et al., 1989, Planta 178, 41–51). There was a close correlation in each case between the levels of the biosynthetic mannosyl- and galactosyltransferases and the deposition of galactomannan. The relative in vitro activities of the mannosyl- and galactosyltransferases in fenugreek and guar were similar, and almost constant throughout the period of galactomannan deposition. In Senna the ratio mannosyltransferase/galactosyltransferase was always higher than in the other two species, and it increased substantially throughout the period of galactomannan deposition. In fenugreek and guar the galactomannans present in the endosperms of seeds at different stages of development had the Man/Gal ratios characteristic of the mature seeds. By contrast the galactomannan present in Senna endosperms at the earliest stages of deposition had a Man/Gal ratio of about 2.3. During late deposition this ratio increased rapidly, stabilising at about 3.3, the ratio characteristic of the mature seed. The levels of α-galactosidase in the developing endosperms of fenugreek and guar were low and remained fairly constant throughout the deposition of the galactomannan. In Senna, α-galactosidase activity in the endosperm was low during early galactomannan deposition, but increased subsequently, peaking during late galactomannan deposition. The developmental patterns of the α-galactosidase activity and of the increase in Man/Gal ratio of the Senna galactomannan were closely similar, indicating a cause-and-effect relationship. The endosperm α-galactosidase activity in Senna was capable, in vitro, of removing galactose from guar galactomannan without prior depolymerisation of the molecule. In fenugreek and in guar the genetic control of the Man/Gal ratio in galactomannan is not the result of a post-depositional modification, and must reside in the biosynthetic process. In Senna, the Man/Gal ratio of the primary biosynthetic galactomannan product is controlled by the biosynthetic process. Yet the final Man/Gal ratio of the galactomannan in the mature seed is, to an appreciable extent, the result of galactose removal from the primary biosynthetic product by an α-galactosidase activity which is present in the endosperm during late galactomannan deposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201625
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Galactomannan formation and guanosine 5′-diphosphate-mannose: galactomannan mannosyltransferase in developing seeds of fenugreek (Trigonella foenum-graecum L., leguminosae) (1982)
    Springer
    Planta 155 (1982), S. 105-111 
    Details
    ISSN: 1432-2048
    Keywords: Galactomannan ; Endosperm ; Polysaccharide (biosynthesis, storage) ; Mannosyltransferase ; Seed (development) ; Trigonella
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The time-course of galactomannan and stachyose (digalactosyl-sucrose) deposition in the fenugreek seed endosperm has been determined, and correlated with standard parameters of seed development. During, and only during, the period of galactomannan deposition, endosperm homogenates are capable of catalysing the transfer of labelled d-mannosyl residues from guanosine 5′-diphosphate d-[U-14C]mannose to a soluble polysaccharide product indistinguishable from galactomannan. The mannosyltransferase activity peaks twice, once at the beginning of galactomannan deposition, and again in the middle of the most rapid phase of galactomannan deposition. The enzyme in the later peak sediments with grossly particulate material (1,000 g pellet), whereas the earlier peak contains a considerable proportion of a particulate enzyme sedimenting at 100,000 g. These observations are discussed in the light of existing information on the ultrastructural aspects of galactomannan deposition. The mannosyltransferase is clearly involved in galactomannan formation in vivo, but the status of an accompanying galactosyltransferase is less clear.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392539
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Changes in cell-wall polysaccharides in relation to seedling development and the mobilisation of reserves in the cotyledons of Lupinus angustifolius cv. Unicrop (1984)
    Springer
    Planta 160 (1984), S. 449-454 
    Details
    ISSN: 1432-2048
    Keywords: Arabinan ; Arabinogalactan ; Cell wall (storage polysaccharides) ; Galactan ; Germination (seeds) ; Hemicellulose ; Lupinus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Some 22% of the dry weight of the cotyledons of resting seeds of Lupinus angustifolius cv. Unicrop has been shown to be non-starch polysaccharide material comprising the massively thickened walls of the storage mesophyll cells. On hydrolysis this material released galactose (76%), arabinose (13%), xylose (4%), uronic acid (7%): only traces of glucose were detected indicating the virtual absence of cellulose from the walls. Changes in the amount and composition of this material following germination have been studied in relation to parameters of seedling development and the mobilisation of protein, lipid and oligosaccharide reserves. Starch, which was not present in the resting seed, appeared transitorily following germination: under conditions of continuous darkness starch levels were reduced. During the period of bulk-reserve mobilisation, 92% of the non-starch polysaccharide material disappeared from the cotyledons. The residual cell-wall material released galactose (14%), arabinose (19%), xylose (24%) and uronic acid (43%). The galactose and arabinose residues of the cotyledonary cell walls clearly constitute a major storage material, quantitatively as important as protein. The overall role of the wall polysaccharides in seedling development is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00429762
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Purification and properties of a novel β-galactosidase or exo-(1 → 4)-β-d-galactanase from the cotyledons of germinated Lupinus angustifolius L. seeds (1994)
    Springer
    Planta 192 (1994), S. 502-511 
    Details
    ISSN: 1432-2048
    Keywords: Galactan ; β-Galactosidase ; Exo-β-galactanase ; Lupinus ; Germination ; Reserve mobilisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The main polysaccharide component of the thickened cell walls in the storage parenchyma of Lupinus angustifolius L. cotyledons is a linear (1 → 4)-β-linked d-galactan, which is mobilised after germination (L.A. Crawshaw and J.S.G Reid, 1984, Planta 160, 449–454). The isolation from the germinated cotyledons of a β-d-galactosidase or exo-(1 → 4)-β-d-galactanase with a high specificity for the lupin galactan is described. The enzyme, purified using diethylaminoethyl-cellulose, carboxymethyl-cellulose and affinity chromatography on lactose-agarose, gave two bands (major 60 kDa, minor 45 kDa) on sodium dodecyl sulphate-gel electrophoresis, and two similar bands on isoelectric focusing (major, pI 7.0, minor pI 6.7, both apparently possessing enzyme activity). The minor component cross-reacted with an antiserum raised against, and affinity-purified on, the major band. Both components had a common N-terminal sequence. The minor component was probably a degradation product of the major one. The enzyme had limited β-galactosidase action, catalysing the hydrolysis of p-nitrophenyl-β-d-galactopyranoside and (1→ 4)- and (1 → 6)-β-linked galactobioses. Lactose [β-d-galactopyranosyl-(1 → 4)-d-glucose] was hydrolysed only very slowly and methyl-β-d-galactopyranoside not at all. Lupin galactan was hydrolysed rapidly and extensively to galactose, whereas other cell-wall polysaccharides (xyloglucan and arabinogalactan) with terminal non-reducing β-d-galactopyranosyl residues were not substrates. A linear (1 → 4)-β-linked galactopentaose was hydrolysed efficiently to the tetraose plus galactose, but further sequential removals of galactose to give the tetraose and lower homologues occurred more slowly. Galactose, γ-galactonolactone and Cu+2 were inhibitory. No endo-β-d-galactanase activity was detected in lupin cotyledonary extracts, whereas exo-galactanase activity varied pari passu with galactan mobilisation. Exo-galactanase protein was detected, by Western immunoblotting of cotyledon extracts, just before the activity could be assayed and then increased and decreased in step with the enzyme activity. The exo-galactanase is clearly a key enzyme in galactan mobilisation and may be the sole activity involved in depolymerising the dominant (1 → 4)-β-galactan component of the cell wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203588
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Enzyme specificity in galactomannan biosynthesis (1995)
    Springer
    Planta 195 (1995), S. 489-495 
    Details
    ISSN: 1432-2048
    Keywords: Biosynthesis (computer simulation) ; Cell wall (plant) ; Cyamopsis ; Galactomannan ; Senna ; Trigonella
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Membrane-bound enzymes from developing legume-seed endosperms catalyse galactomannan biosynthesis in vitro from GDP-mannose and UDP-galactose. A mannosyltransferase [mannan synthase] catalyses the extension of the linear (1→4)-β-linked d-mannan backbone towards the non-reducing end. A specific α-galactosyltransferase brings about the galactosyl-substitution of the backbone by catalysing the transfer of a (1→6)-α-d-galactosyl residue to an acceptor mannosyl residue at or close to the non-reducing terminus of the growing backbone. Labelled galactomannans with a range of mannose/galactose (Man/Gal) ratios were formed in vitro from GDP-[14C]mannose and UDP-[14C]galactose using membrane-bound enzyme preparations from fenugreek (Trigonella foenum-graecum L.), guar (Cyamopsis tetragonoloba (L.) Taub.) and senna (Senna occidentalis (L.) Link.), species which in vivo, form galactomannans with Man/Gal ratios of 1.1, 1.6 and 3.3 respectively. The labelled galactomannans were fragmented using a structure-sensitive endo-(1→4)-β-d-mannanase and the quantitative fragmentation data were processed using a computer algorithm which simulated the above model for galactomannan biosynthesis on the basis of a second-order Markov chain process, and also the subsequent action of the endo-mannanase. For each galactomannan data-set processed, the algorithm generated a set of four conditional probabilities required by the Markov model. The need for a second-order Markov chain description indicated that the galactomannan subsite recognition sequence of the galactosyltransferase must encompass at least three backbone mannose residues, i.e. the site of substitution and the two preceding ones towards the reducing end of the growing galactomannan chain. Data-sets from the three plant species generated three distinctly different sets of probabilities, and hence galactose-substitution rules. For each species, the maximum degree of galactose-substitution consistent with these rules was closely similar to that observed for the primary product of galactomannan biosynthesis in vivo. The data provide insight into the mechanism of action and the spatial organisation of membrane-bound polysaccharide synthases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195705
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Xyloglucan (amyloid) mobilisation in the cotyledons of Tropaeolum majus L. seeds following germination (1985)
    Springer
    Planta 163 (1985), S. 133-140 
    Details
    ISSN: 1432-2048
    Keywords: Amyloid (seed) ; Endo-β-glucanase ; β-Galactosidase ; Germination (seed) ; β-Glucosidase ; Tropaeolum (amyloid mobilisation) ; Xyloglucan ; α-Xylosidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The levels of cell-wall xyloglucan (amyloid) in nasturtium (Tropaeolum majus L.) cotyledons were monitored during a 28-d period covering seed imbibition, germination and early seedling development. The activities of the following enzymes capable of hydrolysing the glycosidic linkages in the xyloglucan were assayed in cotyledon extracts over the same period: endo-(1→4)-β-glucanase (EC 3.2.1.4), β-glucosidase (EC 3.2.1.21), α-xylosidase and β-galactosidase (EC 3.2.1.23). The endo-β-glucanase was assayed viscometrically using xyloglucan as substrate, and the three glycosidases using appropriate p-nitrophenylglycosides. Alpha xylosidase and β-galactosidase, the enzymes which would be expected to hydrolyse the side-chains from the xyloglucan molecule, were also assyed using xyloglucan as substrate. Under our culture conditions, xyloglucan levels remained constant at 30 mg per cotyledon pair for 7 d, that is until 3 d after germination: thereafter, the amount of xyloglucan diminished to zero in a 12-d period. The most rapid period of depletion was between days 9 and 13. The mobilisation of all reserve substances from the cotyledons resulted in a weight-loss of 92 mg: xyloglucan, therefore, is an important storage substance, representing 33% by weight of the seed's substrate reserves. It is a cell-wall storage polysaccharide. Xyloglucan mobilisation was accompanied by a 17-fold increase in endo-β-glucanase activity, a 7-fold increase in β-galactosidase and an 8-fold increase in α-xylosidase activities, all determined using xyloglucan as substrate. All three activities began to increase at day 5, peaked at days 12–14 when the most rapid phase of xyloglucan breakdown was over, and had declined to zero by days 22–25. The levels of theses enzymes have been shown to be consistent with their being responsible for xyloglucan hydrolysis in vivo. Nitrophenyl-β-galactosidase activity increased up to day 3, remained constant and then increased again 2.5-fold from day 5, peaking at day 11. Nitrophenyl-β-glucosidase remained relatively constant up to day 16 and then decreased to zero by day 25. Nitrophenyl-α-xylosidase activity was not detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395907
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Degradation of the endosperm cell walls of Lactuca sativa L., cv. grand rapids in relation to the mobilisation of proteins and the production of hydrolytic enzymes in the axis, cotyledons and endosperm (1979)
    Springer
    Planta 146 (1979), S. 335-341 
    Details
    ISSN: 1432-2048
    Keywords: Endosperm ; Germination (seeds) ; Lactuca ; Reserve hydrolysis ; Storage protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The timing of changes in total nitrogen and soluble amino nitrogen content, and in the activities of proteinase (pH 7.0), isocitrate lyase, catalase, phytase, phosphatase (pH 5.0), α-galactosidase and β-mannosidase were studied in extracts from the cotyledons, axis and endosperms of germinating and germinated light-promoted lettuce seeds. The largest amount of total nitrogen (2.7% seed dry weight) occurs within the cotyledons, as storage protein. As this decreases the total nitrogen content of the axis increases and the soluble amino nitrogen in the cotyledons and axis increases. Proteinase activity in the cotyledons increases coincidentally with the depletion of total nitrogen therein. Enzymes for phytate mobilisation and for gluconeogenesis of hydrolysed lipids increase in activity in the cotyledons as the appropriate stored reserves decline. Beta-mannosidase, an enzyme involved in the hydrolysis of oligo-mannans released by the action of endo-β-mannase on mannan reserves in the endosperm, arises within the cotyledons. This indicates that complete hydrolysis of mannans to the monomer does not occur within the endosperm. Mobilisation of all cotyledon reserves occurs after the endosperm has been degraded, providing further evidence that the endosperm is an early source of food reserves for the growing embryo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387806
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    A dual rôle for the endosperm and its galactomannan reserves in the germinative physiology of fenugreek (Trigonella foenum-graecum L.), an endospermic leguminous seed (1979)
    Springer
    Planta 147 (1979), S. 145-150 
    Details
    ISSN: 1432-2048
    Keywords: Endosperm ; Galactomannan ; Germination (seeds) ; Storage polysaccharide ; Trigonella ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Some 30% of the reserve material in the fenugreek seed is galactomannan localised in the endosperm; the remainder is mainly protein and lipid in the cotyledons of the embryo. The importance of galactomannan to the germinative physiology of fenugreek has been investigated by comparing intact and endosperm-free seeds. From a purely nutritional point of view the galactomannan's rôle is not qualitatively different from that of the food reserves in the embryo. Nevertheless, due to its spatial location and its hydrophilic properties, the galactomannan is the molecular basis of a mechanism whereby the endosperm imbibes a large quantity of water during seed hydration and is able to “buffer” the germinating embryo against desiccation during subsequent periods of drought-stress. The galactomannan is clearly a dual-purpose polysaccharide, regulating water-balance during germination and serving as a substrate reserve for the developing seedling following germination. The relative importance of these two rôles is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389515
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Substrate subsite recognition of the xyloglucan endo-transglycosylase or xyloglucan-specific endo-(1→4)-β-d-glucanase from the cotyledons of germinated nasturtium (Tropaeolum majus L.) seeds (1996)
    Springer
    Planta 200 (1996), S. 221-228 
    Details
    ISSN: 1432-2048
    Keywords: Cell wall (plant) ; Enzyme (specificity) ; Hemicellulose ; Tropaeolum ; Xyloglucan ; Xyloglucanendo-transglycosylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have investigated the substrate subsite recognition requirement of the xyloglucan endo-transglycosylase/xyloglucan-specific endo-(1→4)-β-d-glucanase (NXET) from the cotyledons of nasturtium seedlings. Seed xyloglucans are composed almost entirely of the Glc4 subunits XXXG, XLXG, XXLG and XLLG, where G represents an unsubstituted glucose residue, X a xylose-substituted glucose residue and L a galactosyl-xylose-substituted glucose residue. Thus in the xyloglucan sequence shown below, the xylose (Xyl) residues at the backbone glucose (Glc) residues numbered — 3,— 2, + 2 and + 3 may be galactose-substituted, and NXET cleaves between the unsubstituted glucose at — 1 and the xylose-substituted glucose at + 1, which never carries a galactosyl substituent. We have isolated the xyloglucan oligosaccharides XXXGXXXG and XLLGXLLG from NXET digests of tamarind seed xyloglucan, have modified them enzymatically using a pure xyloglucan oligosaccharide-specific α-xylosidase from nasturtium seeds to give GXXGXXXG and GLLGXLLG, and have identified and compared the products of NXET action on XXXGXXXG, GXXGXXXG, XLLGXLLG and GLLGXLLG. We have also compared the molar proportions of XXXG, XLXG, XXLG and XLLG in native tamarind and nasturtium seed xyloglucans with those in NXET digests of these polysaccharides. Using these and existing data we have demonstrated that NXET action does not require xylosesubstitution at glucose residues — 4, — 2, + 1 and + 3 and that xylose substitution at + 2, is a requirement. There may also be a requirement for xylose substitution at — 3. We have demonstrated also that galactosyl substitution of a xylose residue at + 1 prevents, and at — 2 modifies, chain-cleavage. A partial model for the minimum substrate binding requirement of NXET is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208312
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...