Ribose-5-phosphate (R5P)

Ribose 5-phosphate is both a product and an intermediate of the pentose phosphate pathway. The last step of the oxidative reactions in the pentose phosphate pathway is the production of ribulose-5-phosphate. Depending on the body's state, ribulose-5-phosphate can reversibly isomerize to ribose-5-phosphate.

Ribulose-5-phosphate can alternatively undergo a series of isomerizations as well as transaldolations and transketolations that result in the production of other pentoses phosphates as well as fructose 6-phosphate and glyceraldehyde-3-phosphate (both intermediates in glycolysis). The enzyme ribose-phosphate diphosphokinase converts ribose-5-phosphate into phosphoribosyl pyrophosphate.