Essential for rapid growth and for sporulation. Catalyzes the interconversion of 2-phosphoglycerate and 3-phosphoglycerate. (2R)-2-phosphoglycerate = (2R)-3-phosphoglycerate Binds 2 manganese ions per subunit. Inhibited during sporulation by acidification of the forespore, thus allowing accumulation of the spore's large depot of 3-phosphoglyceric acid. Very sensitive to pH. A pH change from 8 to 6 results in greater than 30- to 200-fold decreases in its activity. However, deactivation at pH 6 is reversed by shifting the enzyme to pH 7 or 8. Carbohydrate degradation; glycolysis; pyruvate from D-glyceraldehyde 3-phosphate: step 3/5. Monomer. Belongs to the BPG-independent phosphoglycerate mutase family.