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Pakistan Journal of Biological Sciences
  Year: 2000 | Volume: 3 | Issue: 5 | Page No.: 892-895
DOI: 10.3923/pjbs.2000.892.895
 
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Starch Synthesis and Carbohydrate Oxidation In Developing Potato Tuber Amyloplasts

Muhammad Naeem , Michael J. Emes and M. Yasin Ashraf

Abstract:
Starch, the major source of calorific intake in the human diet, is synthesised in the amyloplasts of non-photosynthetic tissues. To understand its synthesis, to determine which substrate is taken up by the organelle and which metabolite is broken down for the release of energy, the present studies were started from potato tuber (cv. Record). Glucose 1-phosphate (Glc1P) was the most effective substrate for starch synthesis in amyloplasts. The rate of incorporation of hexose (Glc1P) into starch was dependent on the presence of exogenous ATP and on the intactness of the preparation. Rates of starch synthesis from Glc1P plus ATP were linear for up to 1h and was saturated by 5-10 mM Glc1P. The uptake of Glc1P was inhibited by the addition of exogenous glucose 6-phosphate (Glc6P) and was not effected by the addition of 3-phosphoglyceric acid (3PGA). Other than Glc1P, ADPglucose (ADPG) also supported similar rates of starch synthesis, however, rate was saturated by 1mM ADPG. The import of ADPG and ATP into the amyloplast indirectly indicate the presence of an adenylate translocator on the organelle membrane. Carbohydrate oxidation in the amyloplast was stimulated by the addition of 2-oxoglutarate and glutamine. Glucose 1-phosphate also proved to be a better substrate for oxidative pathways than glucose 6-phosphate. The implications of these results for our understanding of the pathway of starch synthesis and carbohydrate oxidation are discussed.
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How to cite this article:

Muhammad Naeem , Michael J. Emes and M. Yasin Ashraf , 2000. Starch Synthesis and Carbohydrate Oxidation In Developing Potato Tuber Amyloplasts . Pakistan Journal of Biological Sciences, 3: 892-895.

DOI: 10.3923/pjbs.2000.892.895

URL: https://scialert.net/abstract/?doi=pjbs.2000.892.895

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