sedoheptose7phosphate

Sedoheptulose-7-phosphate is a seven-carbon sugar phosphate that plays a crucial role in cellular metabolism. It is an intermediate in the pentose phosphate pathway and the Calvin cycle.

In the pentose phosphate pathway, sedoheptulose-7-phosphate is formed through the transketolase reaction, which converts a five-carbon sugar phosphate (ribulose-5-phosphate) and a two-carbon unit into a seven-carbon sugar phosphate. This pathway is essential for generating NADPH, a reducing agent vital for various biosynthetic processes and for protecting cells against oxidative stress, and for producing precursor metabolites for nucleotide synthesis.

Sedoheptulose-7-phosphate is also a key component of the Calvin cycle, the primary mechanism by which plants and other photosynthetic organisms convert carbon dioxide into sugars. Within the Calvin cycle, sedoheptulose-1,7-bisphosphate is dephosphorylated to yield sedoheptulose-7-phosphate. This molecule then participates in a transketolase reaction to regenerate ribulose-1,5-bisphosphate, the initial CO2 acceptor, thus allowing the cycle to continue.

The presence and metabolism of sedoheptulose-7-phosphate are indicative of active carbon fixation and the operation of the pentose phosphate pathway. Its concentration can be influenced by cellular energy status and the availability of substrates and cofactors. Studying sedoheptulose-7-phosphate and its related enzymes provides insights into the efficiency and regulation of these fundamental metabolic pathways.