Involved in the biosynthesis of kanosamine (3-amino-3-deoxy-D-glucose), which is known to have antibiotic and antifungal properties, and to be a precursor of the antibiotic neotrehalosadiamine (3,3'-diamino-3,3'-dideoxy-alpha,beta-trehalose (NTD)). Catalyzes the dephosphorylation of kanosamine 6-phosphate to yield kanosamine. There is a trace amount of activity using glucosamine-6-phosphate. D-kanosamine 6-phosphate + H2O = kanosamine + phosphate kcat is 32 sec(-1) for dephosphorylation with kanosamine 6-phosphate (at pH 7.5 and 25 degrees Celsius). Antibiotic biosynthesis; kanosamine biosynthesis. Homotetramer. Induced by neotrehalosadiamine. The production of neotrehalosadiamine is dormant in the wild-type strain. A mutation in the beta subunit of RNA polymerase activates the production of the neotrehalosadiamine (PubMed:14612444). Belongs to the HAD-like hydrolase superfamily. Cof family.