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The pentose phosphate route is a metabolic mechanism similar to glycolysis. In addition to ribose 5-phosphate, it also produces NADPH and pentoses.The pathway plays a more anabolic than catabolic role.

Isomerization and epimerization processes proceed in step 2 of the pentose phosphate cycle. In this process, in the presence of the enzyme ribose-5-phosphate isomerase, ribulose-5-phosphate is transformed into ribose-5-phosphate. A broad family of isomerase enzymes catalyzes the interconversion of chemical isomers termed ribose-5-phosphate isomerase. The conversion of ribose-5-phosphate takes place in a reversible mechanism through a 1, 2-enediolate intermediate.

Hence, the ribulose-5-phosphate isomerase transforms ribulose-5-phosphate to ribose-5-phosphate via the enediolate intermediate.