The oxydative pentose phosphate cycle is in many respects the conversion of the reductive pentose phosphate cycle that we know better as the Calvin cycle. We will delve into it in more detail when dealing with photosynthesis. Contrary to the Calvin cycle that takes place in chloroplasts do the reactions of the oxydative pentose phosphate cycle place in the cytosol. Also are its reactions not confined to plant cells alone. The participating enzymes are both transketolases and transaldolases.
Several reactions lead to intermediates that are also intermediates of glycolysis.
They represent links between the pentose phosphate cycle and glycolysis. In the reaction is a ketogroup transferred from one sugar to another intermediate of glycolysis is generated as a by-product. The latter is an intermediate of glycolysis, too, while the first is, as we have already seen, necessary for the synthesis of the amino acids serine and glycine. The supply and the need for them decides whether an intermediate remains in the pentose phosphate cycle or is fed into glycolysis to be degraded. The coupling of both pathways offers also the opportunity to regain glucose.