Catalyzes the conversion of the nucleoside breakdown products ribose-1-phosphate and deoxyribose-1-phosphate to the corresponding 5-phosphopentoses. Catalyzes the interconversion of glucose-1-phosphate into glucose-6-phosphate but with a lower catalytic efficiency. In vitro, has also a low glucose 1,6-bisphosphate synthase activity which is most probably not physiologically relevant. alpha-D-ribose 1-phosphate = D-ribose 5-phosphate 2-deoxy-alpha-D-ribose 1-phosphate = 2-deoxy-D-ribose 5-phosphate alpha-D-glucose 1-phosphate = alpha-D-glucose 6-phosphate Binds 1 Mg(2+) ion per subunit. Highly expressed in lung, spleen and thymus. Expressed at lower levels in liver, brain, kidney, skeletal muscle, testis and heart. Belongs to the phosphohexose mutase family. There is a known reversal of the Pgm1 and Pgm2 nomenclature applied to mouse versus other vertebrates. The official name of this gene in mouse is Pgm1 but it is the ortholog of other vertebrate PGM2 genes.