where the pentose phosphate formed is interconvertible between ribose 5-phosphate, ribulose 5-phosphate and xylulose 5-phosphate.
The later stages of the pathway carried out the reaction:
If six molecules of glucose 6-phosphate undergo the early stages, and if the 6 molecules of pentose 5-phosphate formed are converted into 5 molecules of glucose 6-phosphate + phosphate in the later stages, then the net overall reaction will be:
i.e. effectively complete oxidation of glucose 6-phosphate to CO2 with generation of NADPH for fat synthesis, etc. The scheme below shows how this conversion of six molecules of pentose phosphate into five molecules of glucose 6-phosphate is achieved.
© IUBMB 2003
The [C2] and [C3] units are transferred from a ketose to an aldose by EC 220.127.116.11, transketolase, and EC 18.104.22.168, transaldolase, respectively.
pentose pathway (early stages)
pentose pathway (later stages)
EC 22.214.171.124 transketolase (mechanism)
EC 126.96.36.199 transaldolase (mechanism)
EC 188.8.131.52 fructose-bisphosphatase
EC 184.108.40.206 fructose-bisphosphate aldolase
EC 220.127.116.11 triose-phosphate isomerase
EC 18.104.22.168 glucose-6-phosphate isomerase