Soluble invertase was purified from pea （Pisum sativum L.） by sequential procedures entailing ammonium sulfate precipitation, DEAE-Sepharose column, Con-A- and Green 19-Sepharose affinity columns, hydroxyapatite col...Soluble invertase was purified from pea （Pisum sativum L.） by sequential procedures entailing ammonium sulfate precipitation, DEAE-Sepharose column, Con-A- and Green 19-Sepharose affinity columns, hydroxyapatite column, ultra-filtration, and Sephacryl 300 gel filtration. The purified soluble acid （SAC） and alkaline （SALK） invertases had a pH optimum of 5.3 and 7.3, respectively. The temperature optimum of two invertases was 37 ℃. The effects of various concentrations of Tris-HCI, HgCI2, and CuSO4 on the activities of the two purified enzymes were examined. Tris-HCI and HgCI2 did not affect SAC activity, whereas 10 mM Tris-HCI and 0.05 mM HgCI2 inhibited SALK activity by about 50%. SAC and SALK were inhibited by 4.8 mM and 0.6 mM CuSO4 by 50%, respectively. The enzymes display typical hyperbolic saturation kinetics for sucrose hydrolysis. The Kms of SAC and SALK were determined to be 1.8 and 38.6 mM, respectively. The molecular masses of SAC shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting were 22 kDa and 45 kDa. The molecular mass of SALK was 30 kDa. Iso-electric points of the SAC and SALK were estimated to be about pH 7.0 and pH 5.7, respectively.展开更多
: The soluble acid invertase (SAI) and cell wall-bound invertase (CWI) were purified from apple fruit to apparent electrophoretic homogeneity. Based on sequencing, substrate specificity, and immunoblotting assay, the ...: The soluble acid invertase (SAI) and cell wall-bound invertase (CWI) were purified from apple fruit to apparent electrophoretic homogeneity. Based on sequencing, substrate specificity, and immunoblotting assay, the purified enzymes were identified to be two isoforms of acid invertase (β-fructosidase; EC 3.2.1. 26). The SAI and CWI have the same apparent molecular mass with a holoenzyme of molecular mass of 220 kDa composed of 50 kDa subunits. The SAI has a lower Km value for sucrose and higher Km for raffinose compared with CWI. These acid invertases differ from those in other plants in some of their biochemical properties, such as the extremely high Km value for raffinose, no hydrolytic activity for stachyose, and a mixed form of inhibition by fructose to their activity. The antibodies directed against the SAI and CWI recognized, from the crude extract, three polypeptides with a molecular mass of 50, 68, and 30 kDa, respectively. These results provide a substantial basis for the further studies of the acid invertases in apple fruit.展开更多
The effect of water deficit on stem reserve mobilization and sink activity in wheat (Triticum aestivum L.) cultivars, viz., C306 (drought tolerant) and PBW343 (drought sensitive) was studied. Drought was maintained in...The effect of water deficit on stem reserve mobilization and sink activity in wheat (Triticum aestivum L.) cultivars, viz., C306 (drought tolerant) and PBW343 (drought sensitive) was studied. Drought was maintained in pot raised plants by withholding irrigation at 95 days after sowing (DAS), i.e. just five days before the initiation of anthesis. Drought induced a significant reduction in mean biomass of all the internodes of sensitive cultivar as compared to those of tolerant one. Mobilized dry matter and mobilization efficiency were observed to be higher in the internodes of tolerant cultivar, both under control and stress conditions, which resulted in enhanced translocation of stem reserves to the grains. Water soluble carbohydrates (WSC), which mainly occur as fructans, were observed to be higher in the internodes of tolerant cultivar than those of sensitive one. When drought was applied, fructans were mobilized more effectively from the internodes of tolerant cultivar. A significantly higher sucrose synthase activity in the grains of tolerant cultivar, under drought conditions, increased the sink strength by unloading the assimilates in the sink, thereby increasing further mobilization of assimilates to the grains. Grains of sensitive cultivar attained maturity much earlier as compared to the tolerant one, both under control and stress conditions. The longer duration of grain maturation in tolerant cultivar supported enhanced mobilization of stem reserves, thus restricting heavy decrease in grain yield, under stress conditions, as compared to the sensitive cultivar. It may, therefore, be concluded that certain characteristics viz., enhanced capability of fructan storage, higher mobilization efficiency, stronger sink activity and longer duration of grain maturation might help the drought tolerant cultivar in coping the stress展开更多
Six rice varieties, PR120, PR116, Feng Ai Zan, PR115, PAU201 and Punjab Mehak 1 were raised under aerobic and transplanting conditions to assess the effects of planting conditions on sucrose metabolising enzymes in re...Six rice varieties, PR120, PR116, Feng Ai Zan, PR115, PAU201 and Punjab Mehak 1 were raised under aerobic and transplanting conditions to assess the effects of planting conditions on sucrose metabolising enzymes in relation to the transformation of free sugars to starch and protein in flag leaves and grains. Activities of sucrose synthase, sucrose phosphate synthase and acid invertase increased till flowering stage in leaves and mid-milky stage（14 d after flowering） in grains and thereafter declined in concomitant with the contents of reducing sugar. Under aerobic conditions, the activities of acid invertase and sucrose synthase（cleavage） significantly decreased in conjunction with the decrease in non-reducing sugars and starch content in all the varieties. Disruption of starch biosynthesis under the influence of aerobic conditions in both leaves and grains and the higher build up of sugars possibly resulted in their favoured utilization in nitrogen metabolism. Feng Ai Zan, PR115 and PR120 maintained higher levels of sucrose synthase enzymes in grains and leaves and contents of metabolites（amino acid, protein and non-reducing sugar） under aerobic conditions, while PR116, Punjab Mehak 1 and PAU201 performed better under transplanting conditions, thus showing their adaptation to environmental stress. Yield gap between aerobic and transplanting rice is attributed primarily to the difference in sink activity and strength. Overall, it appear that up-regulation of sucrose synthase（synthesis） and sucrose phosphate synthase under aerobic conditions might be responsible in enhancing growth and productivity of rice varieties.展开更多
基金supported by grants from the Korea Ocean Research & Development Institute (PE98474)by grants from BioGreen 21 Project funded by Rural Development Administration of Korea (20070401-034-028-009)
文摘Soluble invertase was purified from pea （Pisum sativum L.） by sequential procedures entailing ammonium sulfate precipitation, DEAE-Sepharose column, Con-A- and Green 19-Sepharose affinity columns, hydroxyapatite column, ultra-filtration, and Sephacryl 300 gel filtration. The purified soluble acid （SAC） and alkaline （SALK） invertases had a pH optimum of 5.3 and 7.3, respectively. The temperature optimum of two invertases was 37 ℃. The effects of various concentrations of Tris-HCI, HgCI2, and CuSO4 on the activities of the two purified enzymes were examined. Tris-HCI and HgCI2 did not affect SAC activity, whereas 10 mM Tris-HCI and 0.05 mM HgCI2 inhibited SALK activity by about 50%. SAC and SALK were inhibited by 4.8 mM and 0.6 mM CuSO4 by 50%, respectively. The enzymes display typical hyperbolic saturation kinetics for sucrose hydrolysis. The Kms of SAC and SALK were determined to be 1.8 and 38.6 mM, respectively. The molecular masses of SAC shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting were 22 kDa and 45 kDa. The molecular mass of SALK was 30 kDa. Iso-electric points of the SAC and SALK were estimated to be about pH 7.0 and pH 5.7, respectively.
文摘: The soluble acid invertase (SAI) and cell wall-bound invertase (CWI) were purified from apple fruit to apparent electrophoretic homogeneity. Based on sequencing, substrate specificity, and immunoblotting assay, the purified enzymes were identified to be two isoforms of acid invertase (β-fructosidase; EC 3.2.1. 26). The SAI and CWI have the same apparent molecular mass with a holoenzyme of molecular mass of 220 kDa composed of 50 kDa subunits. The SAI has a lower Km value for sucrose and higher Km for raffinose compared with CWI. These acid invertases differ from those in other plants in some of their biochemical properties, such as the extremely high Km value for raffinose, no hydrolytic activity for stachyose, and a mixed form of inhibition by fructose to their activity. The antibodies directed against the SAI and CWI recognized, from the crude extract, three polypeptides with a molecular mass of 50, 68, and 30 kDa, respectively. These results provide a substantial basis for the further studies of the acid invertases in apple fruit.
文摘The effect of water deficit on stem reserve mobilization and sink activity in wheat (Triticum aestivum L.) cultivars, viz., C306 (drought tolerant) and PBW343 (drought sensitive) was studied. Drought was maintained in pot raised plants by withholding irrigation at 95 days after sowing (DAS), i.e. just five days before the initiation of anthesis. Drought induced a significant reduction in mean biomass of all the internodes of sensitive cultivar as compared to those of tolerant one. Mobilized dry matter and mobilization efficiency were observed to be higher in the internodes of tolerant cultivar, both under control and stress conditions, which resulted in enhanced translocation of stem reserves to the grains. Water soluble carbohydrates (WSC), which mainly occur as fructans, were observed to be higher in the internodes of tolerant cultivar than those of sensitive one. When drought was applied, fructans were mobilized more effectively from the internodes of tolerant cultivar. A significantly higher sucrose synthase activity in the grains of tolerant cultivar, under drought conditions, increased the sink strength by unloading the assimilates in the sink, thereby increasing further mobilization of assimilates to the grains. Grains of sensitive cultivar attained maturity much earlier as compared to the tolerant one, both under control and stress conditions. The longer duration of grain maturation in tolerant cultivar supported enhanced mobilization of stem reserves, thus restricting heavy decrease in grain yield, under stress conditions, as compared to the sensitive cultivar. It may, therefore, be concluded that certain characteristics viz., enhanced capability of fructan storage, higher mobilization efficiency, stronger sink activity and longer duration of grain maturation might help the drought tolerant cultivar in coping the stress
文摘Six rice varieties, PR120, PR116, Feng Ai Zan, PR115, PAU201 and Punjab Mehak 1 were raised under aerobic and transplanting conditions to assess the effects of planting conditions on sucrose metabolising enzymes in relation to the transformation of free sugars to starch and protein in flag leaves and grains. Activities of sucrose synthase, sucrose phosphate synthase and acid invertase increased till flowering stage in leaves and mid-milky stage（14 d after flowering） in grains and thereafter declined in concomitant with the contents of reducing sugar. Under aerobic conditions, the activities of acid invertase and sucrose synthase（cleavage） significantly decreased in conjunction with the decrease in non-reducing sugars and starch content in all the varieties. Disruption of starch biosynthesis under the influence of aerobic conditions in both leaves and grains and the higher build up of sugars possibly resulted in their favoured utilization in nitrogen metabolism. Feng Ai Zan, PR115 and PR120 maintained higher levels of sucrose synthase enzymes in grains and leaves and contents of metabolites（amino acid, protein and non-reducing sugar） under aerobic conditions, while PR116, Punjab Mehak 1 and PAU201 performed better under transplanting conditions, thus showing their adaptation to environmental stress. Yield gap between aerobic and transplanting rice is attributed primarily to the difference in sink activity and strength. Overall, it appear that up-regulation of sucrose synthase（synthesis） and sucrose phosphate synthase under aerobic conditions might be responsible in enhancing growth and productivity of rice varieties.
