Catalyzes the conversion of adenosine monophosphate (AMP) to inosine monophosphate (IMP) and ammonia (NH4(+)) (PubMed:11784104, PubMed:1916064). Participates in the regulation of the adenylated nucleotide pool and the interconversion to guanylated nucleotides during early morphodifferentiation (PubMed:1916064, PubMed:17259634). AMP + H(+) + H2O = IMP + NH4(+) Binds 1 zinc ion per subunit. Activated by ATP, inhibited by GTP, EDTA and inorganic phosphate. Purine metabolism; IMP biosynthesis via salvage pathway; IMP from AMP: step 1/1. Homodimer. Expressed during normal growth and slightly more for the first 4 hours of development. Enzymatic activity increases for the first 5 hours of development and then tapers off. Cells grow normally until development occurs. Then they make a significantly increased proportion of prestalk cells, and develop fruiting bodies with short thick stalks and glassy sori with less than 5% normal spores. They have an increased content of pstA-type prestalk cells. Intracellular levels of inosine increase dramatically during development. This is cell autonomous, as the presence of equal numbers of wild-type cells does not alter the cell type proportion nor improve sporulation. Overexpression of the gene has no apparent effect on development (PubMed:11784104). Mutants lacking amdA form aspidocytes (a cell type able to resist detergent lysis and which are also resistant to some antibiotics) more readily than wild-type cells; their induction may involve AMP or other purine metabolites (PubMed:17259634). Belongs to the metallo-dependent hydrolases superfamily. Adenosine and AMP deaminases family.