Sedoheptulose

A heptose sugar involved in metabolic pathways

Sedoheptulose is a seven-carbon ketose sugar, also known as a heptose, with the chemical formula C₇H₁₄O₇. It plays a significant role in various metabolic pathways, particularly in the pentose phosphate pathway and the Calvin cycle in plants.

Structure

Sedoheptulose is a monosaccharide with a seven-carbon backbone. It is classified as a ketose because it contains a ketone group at the second carbon atom. The structure of sedoheptulose can be represented in both linear and cyclic forms, with the cyclic form being more prevalent in biological systems.

Biological Role

Sedoheptulose is an important intermediate in the pentose phosphate pathway, a metabolic pathway parallel to glycolysis. This pathway is crucial for the production of NADPH and ribose-5-phosphate, which are essential for anabolic reactions and nucleotide synthesis, respectively.

In the Calvin cycle, which occurs in the chloroplasts of plant cells, sedoheptulose-7-phosphate is an intermediate that is involved in the regeneration of ribulose-1,5-bisphosphate, a molecule necessary for the fixation of carbon dioxide.

Metabolic Pathways

Pentose Phosphate Pathway

In the pentose phosphate pathway, sedoheptulose-7-phosphate is formed from the reaction between ribose-5-phosphate and xylulose-5-phosphate catalyzed by the enzyme transketolase. This reaction is reversible and plays a key role in the non-oxidative phase of the pathway.

Calvin Cycle

In the Calvin cycle, sedoheptulose-7-phosphate is produced from the reaction between erythrose-4-phosphate and dihydroxyacetone phosphate catalyzed by the enzyme aldolase. It is then converted to ribulose-5-phosphate through a series of reactions, ultimately contributing to the regeneration of ribulose-1,5-bisphosphate.

Clinical Significance

While sedoheptulose itself is not directly associated with any specific diseases, its role in the pentose phosphate pathway and the Calvin cycle makes it a critical component of cellular metabolism. Disruptions in these pathways can lead to metabolic disorders and affect cellular growth and function.

Research and Applications

Research into sedoheptulose and its derivatives is ongoing, particularly in the context of metabolic engineering and synthetic biology. Understanding its role in metabolic pathways can lead to advancements in biofuel production, agricultural biotechnology, and the development of therapeutic strategies for metabolic diseases.

Also see

• Pentose phosphate pathway
• Calvin cycle
• Monosaccharide
• Ketose
• Transketolase
• Aldolase