The function of PGAM2 : Interconversion of 3- and 2-phosphoglycerate with 2,3- bisphosphoglycerate as the primer of the reaction. It can also catalyze the reaction of EC 5.4.2.4 (synthase) and EC 3.1.3.13 (phosphatase), but with a reduced activity.In mammals, the enzyme subunits appear to be either a muscle-derived form (m-type) or other tissue (b-type for brain where the b-isozyme was originally isolated). Existing as a dimer, the enzyme then has 3 isozymes depending on which subunit forms makeup the whole molecule (mm, bb or mb). The mm-type is found mainly in smooth muscle almost exclusively. The mb-isozyme is found in cardiac and skeletal muscle and the bb-type is found in the rest of tissues. While all three isozymes may be found in any tissue, the above distributions are based on prevalence in each.