Catalyzes the dephosphorylation of intracellular maltose 6'-P formed during PTS-catalyzed maltose transport, leading to the formation of maltose. MapP connects PTS-mediated maltose uptake to maltose phosphorylase-catalyzed metabolism. Is also able to efficiently dephosphorylate turanose 6'-P, and to a much lesser extent, leucrose 6'-P and maltulose 6'-P. Cannot use glucose 6-P, fructose 6-P and sucrose 6-P as substrates. alpha-maltose 6'-phosphate + H2O = D-maltose + phosphate kcat is 128 sec(-1). Cells lacking this gene grow significantly and reproducibly faster than the wild-type strain on glucose as carbon source. They are able to transport maltose and grow in maltose-containing medium, although at significantly slower rate than the wild-type strain. They seem to accumulate primarily maltose 6'-P when exposed to a maltose-containing growth medium.