InterPro domain: IPR004788

Ribose 5-phosphate isomerase, also known as phosphoriboisomerase, catalyses the reversible conversion of D-ribose 5-phosphate to D-ribulose 5-phosphate, the first step in the non-oxidative branch of the pentose phosphate pathway [ 1 ]. This reaction enables ribose to be synthesized from sugars, as well as the recycling of sugars during the degradation of nucleotides. There are two unrelated types of ribose 5-phosphate isomerases: type A (RpiA) is the most common and is found in most organisms, while type B (RpiB) is restricted to specific eukaryotic and prokaryotic species. Escherichia coli produces both RpiA and RpiB (also known as AlsB), although RpiA accounts for 99% of total RPI enzymes [ 2 ].

This entry represents type A (RpiA) enzymes found in eukaryotes (plants, Metazoa and fungi), bacteria and archaea.

1. Structure of Escherichia coli ribose-5-phosphate isomerase: a ubiquitous enzyme of the pentose phosphate pathway and the Calvin cycle. Structure 11, 31-42
2. Crystal structure of D-ribose-5-phosphate isomerase (RpiA) from Escherichia coli. Proteins 48, 737-40