Disclosed herein is a transglutaminase inhibitor comprising glucosamine or a derivative thereof. Exhibiting potent inhibitory activity against transglutaminase, the overexpression of which is responsible for the etiology of various diseases, glucosamine or derivatives thereof can be useful in the prevention and treatment of such diseases. Also, a pharmaceutical composition comprising glucosamine or a derivative thereof as an active ingredient and a method of inhibiting transglutaminase are disclosed. Featuring the use of the pharmaceutical composition, the method can be therapeutically safely and effectively-applied to patients afflicted with such diseases.
