Bacterial phosphopentomutases (PPMs) are alkaline phosphatase superfamily members that interconvert alpha-D-ribose 5-phosphate (ribose 5-phosphate) and alpha-D-ribose 1-phosphate (ribose 1-phosphate). This reaction bridges glucose metabolism and RNA biosynthesis. PPM is a Mn(2+)-dependent enzyme and protein phosphorylation activates the enzyme.