Nitrogen Mobilization and Proteolytic Activities in Germinating and Maturing Bush Beans (Phaseolus vulgarisPhaseolus vulgaris L.) (original) (raw)
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Zeitschrift für Naturforschung C, 2006
The protein mobilization from attached and detached seeds of Vicia faba L. cv. Eresen 87 (Fabaceae) was investigated. While the total soluble protein content decreased, the free amino acid content increased during the 7 days germination period. Among the three proteolytic enzymes, only endopeptidase activity was found to be affected by the removal of the embryonic axis. Leucine aminopeptidase activity was high at the beginning, then it decreased; carboxypeptidase activity reached the highest value at day 5. In order to examine the effects of plant growth regulators on detached cotyledons incubated with plant growth regulators [10 Ð4 m benzyladenine (BA), gibberellic acid (GA 3 ), indole acetic acid (IAA) and 10 Ð5 m abscisic acid (ABA)], only benzyladenine was found promotive on protein mobilization. Our results suggest that the removal of the embryonic axis in seeds of Vicia faba L. cv. Eresen 87 decreases protein mobilization and endopeptidase activity.
Physiologia Plantarum, 2001
Removal of the embryonic axis prevents the normal decline of and throughout the entire time from removal of the axis. The carboxypeptidase (Cpase) I in mung bean seedling cotyledons. difference between detached cotyledons in the absence and presence of calcium was greatest when the cotyledons were Cpase I activity and protein, the latter manifested on western detached 4 -6 days after seed imbibition. Loss of Cpase I blots, almost completely disappear about 24 h before the activity and protein can be demonstrated in vitro, with the cotyledon abscises. Of the 3 proteolytic enzyme patterns, only that of Cpase I can be restored by an exogenous supply of 10 maximum level of Cpase I-degrading activity measured 4 days mM CaCl 2 in the agar growth medium. The calcium effect is after seed imbibition under the same growth conditions used to study the calcium effect. It is sensitive to pepstatin and has a dependent on [CaCl 2 ] and is not manifested in the presence of pH optimum of 3, suggesting that this Cpase I-degrading chelators and calcium channel blockers. For detached cotyledons to show the normal low level of Cpase I by the eighth day activity is due to an aspartic protease. of growth, calcium had to be supplied during seed imbibition
Effects of the germination time on enzyme stabilities in extracts from wheat endosperms
Botanica Helvetica, 1986
Salgö A. and Feller U. 1986. Effects of the germination time on enzyme stabilities in extracts from wheat endosperms. Bot. Helv. 96:273-282. Seeds of wheat (Triticum aestivum L.) were germinated and endosperm samples were harvested at daily intervals. Various enzymes were investigated with respect to their stability "in vitro" and their suseeptibility to proteolytic inactivation by endopeptidase activity, which increases during germination. The stability of some enzymes in endosperm extracts was not obviously influenced by germination time (e.g. acid Phosphatase, phytase, peroxidase, malate dehydrogenase). A decreasing stability during germination was observed for leucine aminopeptidase, pyrophosphatase and glucose-6-phosphate dehydrogenase. It appears likely that the accelerated inactivation of these enzymes in endosperm extracts from germinated wheat seeds was caused by the increased endopeptidase activity. Especially glucose-6-phosphate dehydrogenase can be considered as an interesting model enzyme to study proteolytic inactivation and its regulation.
Regulation of reserve protein metabolism in the cotyledons of mung bean seedlings
Proceedings of the National Academy of Sciences, 1976
Seedling growth in mung beans ( Phaseolus aureus , Roxb.) is accompanied by the metabolism of the reserve proteins, and the appearance in the cotyledons of a proteolytic enzyme with endopeptidase activity. Enzyme activity increases 25-fold during the first 5 days of growth. Cotyledon extracts prepared from seeds imbibed for 24 hr with water do not react with rabbit endopeptidase antiserum, which suggests that the enzyme is not present in the seeds as a zymogen. Labeling experiments show that the enzyme is synthesized in the course of seedling growth. The endopeptidase is localized in the protein bodies, and the specific activity of the enzyme in these organelles increases 30-fold. Ultrastructural studies show that the rough endoplasmic reticulum proliferates and may give rise to vesicles which fuse with the protein bodies prior to reserve protein digestion. These vesicles could be the primary lysosomes which transport the enzyme from its site of synthesis to its site of action.
Biochemie und Physiologie der Pflanzen, 1992
Leaf senescence and nitrogen remobilization in field grown wheat can be affected by steamgirdling (phloem interruption). The peduncle (below the ear) or the base of the flag leaf was steamgirdled 1 or lOd after anthesis. Protein contents, free amino acids and peptide hydrolase activities were analyzed throughout the maturing period in extracts of the flag leaf lamina from treated plants and untreated controls. Phloem interruption at the leaf base initiated a rapid net degradation of proteins and an accumulation of free amino acids (mainly glutamine and proline). Azocaseinase activity at pH 5.0 increased during the first week after this treatment and declined afterwards, while the activity at pH 9.0 peaked late during senescence when most of the leaf proteins were already hydrolyzed. Aminopeptidase activities (measured with 8 different substrates) remained at the original level for about one week before they decreased. From this time course it appears possible that aminopeptidases contributed to the complete degradation of leaf proteins. Steam-girdling below the ear slightly delayed the remobilization of proteins in the flag leaf lamina, the increase in endopeptidase and the decrease in aminopeptidase activities. The contents of free amino acids remained higher than in untreated controls. The catabolism of leaf proteins and the pattern of peptide hydrolases were differently influenced by the two treatments.
Plant and Cell Physiology
Nitrogen mobilization and the pattern of proteolytic enzymes were investigated in leaves and glumes of field-grown winter wheat (Triticum aestivum L.) during maturation. Source/sink relations were changed by removal of the ear, the flag leaf or the lower leaves shortly after anthesis. Removal of the ear was most effective, resulting in delayed senescence of the flag leaf with the chlorophyll, aminopeptidase and carboxypeptidase activities remaining high in contrast to the control, whereas neutral endopeptidase activity increased more slowly. No major changes were observed in the second leaf from the top in plants with either ears or flag leaves removed. Nitrogen mobilization and proteolytic activities in glumes and the remaining leaves were influenced only slightly by leaf removal. In earless plants, nitrogen was transported from the second leaf into the leaf sheath and stem, but in the flag leaf the total reduced nitrogen remained high and free amino groups increased. The increase in endopeptidase activity was influenced by the source/sink relations. However, the accumulation of amino groups and the increasing endopeptidase activity in the flag leaf of earless plants suggest that the nitrogen sink capacity did not greatly control protein degradation; it remains to be seen whether phytohormones, accumulated amino acids or other factors delayed the increase in endopeptidase activity.
New serine carboxypeptidase in mung bean seedling cotyledons
Journal of Plant Physiology, 2003
Two serine carboxypeptidases (EC 3.4.16.5) were purified from mung bean seedling cotyledons. Sequences of tryptic peptides derived from the 42.5 kD enzyme corresponded to the derived amino acid sequence of a sequenced cDNA (GenBank U49382 and U49741). This enzyme exhibited the substrate specificity pattern previously published for mung bean carboxypeptidase I. In comparison, the sequence and substrate specificity data obtained for the 43 kD enzyme were similar but not identical. Both enzymes showed preference for peptide substrates with a large hydrophobic residue at the C-terminus. With regard to the penultimate residue of peptide substrates, the mung bean carboxypeptidase I preferred small aliphatic amino acid residues, while the 43 kD enzyme preferred large hydrophobic ones.
Rapid micro methods for the determination of exo- and endopeptidase activities in plant extracts
Microchemical Journal, 1987
Rapid and sensitive photometric assays for aminopeptidase, carboxypeptidase, and endopeptidase activities were developed. The methods of aminopeptidase and carboxypeptidase determinations were based on the hydrolysis of artificial substrates (L-leucine-p-nitroanilide and N-carbobenzoxy-L-phenylalanine+alanine, respectively). Endopeptidase activities were assayed either with acetylated casein or with azocasein as substrate. The utilization of microtitration plates and of a multichannel photometer allowed rapid, sensitive, and accurate measurements. The amounts of enzyme extract and of substrates were reduced considerably compared with other methods for the detection of peptide hydrolase activities. The methods described are suitable for routine measurements in large series (e.g., elution profiles from columns, screening procedures).
Journal of The Science of Food and Agriculture, 2001
The objective of the present work was to determine the impact of nitrogen deficiency on proline metabolism in order to use this amino acid as a bioindicator of the N status of the pods and seeds of French bean (Phaseolus vulgaris L cv Strike) plants. We also identify the pathway of proline synthesis which is favoured under our experimental conditions. N was applied to the nutrient solution in the form of NH4NO3 at 1.45 mM (N1), 2.90 mM (N2) and 5.80 mM (N3, optimal level). Our results indicate that N deficiency is characterised by a decline in proline accumulation in both the pod and the seed, fundamentally because proline degradation is encouraged by stimulation of the enzyme proline dehydrogenase under these conditions. However, although the enzymes in charge of proline biosynthesis (ornithine-δ-aminotransferase and Δ1-pyrroline-5-carboxylate synthetase) vary in behaviour depending on the N status, this amino acid appeared to be synthesised mainly by the enzyme ornithine-δ-aminotransferase, suggesting predominance of the ornithine pathway over the glutamine pathway. Finally, under our experimental conditions, proline can be regarded as a good indicator of N deficiency, particularly in the seeds of French bean plants.© 2001 Society of Chemical Industry