A comparative developmental pattern of enzymes of carbon metabolism and pentose phosphate pathway in mungbean and lentil nodules |
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Authors: | Chopra Jyoti Kaur Narinder Gupta Anil K |
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Institution: | (1) Department of Biochemistry, Punjab Agricultural University, 141 004 Ludhiana |
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Abstract: | The activities of enzymes of pentose phosphate pathway (PPP) viz. glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and carbon metabolism viz. phosphoenol pyruvate carboxylase, NADP- isocitrate dehydrogenase and NADP-malic enzyme were measured in the plant and bacteroid
fractions of mungbean (ureide exporter) and lentil (amide exporter) nodules along with the developing roots for comparison.
The enzymes of pentose phosphate pathway in legume cytosol had higher activities at a stage of maximum nitrogenase activity
and higher sucrose metabolism. However, bacteroids had only limited capacity for this pathway. The specific activities of
these enzymes were greater in ureide than in amide exporter. CO2 fixation via higher activity of phosphoenolpyruvate carboxylase in the plant part of the nodules in lentil might have been due to the
greater synthesis of four carbon amino acids for amide export. The peak of NADP-isocitrate dehydrogenase in both legumes coincided
with the pentose phosphate pathway enzymes at the time of high rates of sucrose metabolism and nitrogen fixation. Higher activities
of NADP-malic enzyme were obtained in mungbean than in the lentil nodules. These findings are consistent with the role of
these enzymes in providing reductant (NADPH) and substrates for energy yielding metabolism of bacteroids and carbon skeletons
for ammonia assimilation. |
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Keywords: | Lens culinaris Vigna radiata Leguminosae lentil mungbean pentose phosphate pathway CO2 assimilation enzymes bacteroids nodules |
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