Absolutely required for the growth of E.coli in a high-phosphate medium containing G-1-P as the sole carbon source. alpha-D-glucose 1-phosphate + H2O = D-glucose + phosphate Independent from inorganic phosphate availability, and apparently submitted to catabolite repression, it is positively controlled by cAMP and the cAMP receptor protein. Optimum pH is about 4. Homodimer. Belongs to the histidine acid phosphatase family.