Catalyzes the interconversion between the alpha and beta anomers from at least three hexose 6-phosphate sugars (Glc6P, Gal6P, and Man6P). alpha-D-glucose 6-phosphate = beta-D-glucose 6-phosphate Present with 8580 molecules/cell in log phase SD medium. Belongs to the glucose-6-phosphate 1-epimerase family.