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Ribose. An oxidation product of glucose 6-phosphate in microsomal fraction
Abstract:
An oxidative metabolism of glucose 6-phosphate was studied in rat liver microsomal fraction. Although radioactive 14CO2 was formed from [1-14C]glucose 6-phosphate in the microsomal fraction (Hino, Y., and Minakami, S. (1982) J. Biochem. (Tokyo) 92, 547-557), the formation was negligible when [2-14C]glucose 6-phosphate was used as a starting substrate. These results indicated an inability of the microsomal fraction to rearrange [2-14C]glucose 6-phosphate to form [1-14C] glucose 6-phosphate, and it was expected that a certain compound derived from glucose 6-phosphate accumulated as an end-product of the reaction. We, therefore, have tried to identify the product by high performance liquid chromatography, and found that ribose accumulated as the end-product. The formation of ribose was inhibited in the same manner as that of 14CO2 by antibodies against rat liver microsomal hexose-6-phosphate dehydrogenase, and the ratios of ribose to 14CO2 formed in the reaction were 0.5-0.8 on a molar basis. The finding of ribose formation further suggested the involvement of ribose phosphate isomerase and phosphatase activities in the reaction.
Insights
Rat liver microsomes metabolize glucose 6-phosphate, producing ribose as an end-product. This pathway involves hexose-6-phosphate dehydrogenase and suggests ribose phosphate isomerase and phosphatase activity.
Area of Science:
- Biochemistry
- Cellular Metabolism
Background:
- Glucose 6-phosphate is a central metabolite in cellular energy pathways.
- Rat liver microsomes possess enzymatic machinery for glucose 6-phosphate metabolism.
Purpose of the Study:
- To elucidate the oxidative metabolism of glucose 6-phosphate in rat liver microsomes.
- To identify the end-product of this metabolic pathway.
Main Methods:
- Utilized radiolabeled [1-14C]glucose 6-phosphate and [2-14C]glucose 6-phosphate as substrates.
- Employed high-performance liquid chromatography (HPLC) for product identification.
- Used antibodies against rat liver microsomal hexose-6-phosphate dehydrogenase for inhibition studies.
Main Results:
- Formation of radioactive 14CO2 from [1-14C]glucose 6-phosphate was observed.
- Negligible 14CO2 formation from [2-14C]glucose 6-phosphate indicated an inability to rearrange the substrate.
- Ribose was identified as the accumulated end-product.
- Ribose formation was inhibited by antibodies against hexose-6-phosphate dehydrogenase.
- Molar ratios of ribose to 14CO2 ranged from 0.5-0.8.
Conclusions:
- Rat liver microsomes metabolize glucose 6-phosphate to produce ribose.
- The pathway involves hexose-6-phosphate dehydrogenase, ribose phosphate isomerase, and phosphatase activities.
- This study identifies a novel metabolic route for glucose 6-phosphate in liver microsomes.