The nucleoside breakdown product ribose-1-phosphate (R1P) can be used to produce energy during oxidative or mitochondrial stress to minimize or delay stress-induced damage. Two steps connect this nucleoside breakdown product to central carbon metabolism in mammals. In the first step, R1P is isomerised to the corresponding 5-phosphopentose, R5P, mediated by phosphoglucomutase-2 (PGM2). PGM2 is a cytosolic, M2+-dependent enzyme that acts ten times better as a phosphopentomutase (both on R1P and dR1P) than as a phosphoglucomutase (on glucose-1-phosphate) (Maliekal et al. 2007).