[Characteristics of gamma glutamyl transferase in melanoma]

Gamma glutamyl transferase (GGT) is widely distributed in mammalian tissues, and its biological heterogeneity has been demonstrated among various tissues. In order to investigate the biological characteristics of GGT in melanomas, enzyme-histochemical and biochemical studies were performed using amelanotic/melanotic and murine/human melanomas as materials. Enzyme-histochemically, GGT activity appeared to be present only in melanogenic cells in vitro. Biochemical assays of tissue extracts revealed that the specific activity was much higher in melanotic melanomas than in amelanotic. In addition, analysis of GGT-isoenzymes demonstrated that an isoenzyme band at approximately 110KD was expressed in tumorigenic or highly-metastatic tissues. These findings suggest that GGT in melanoma is closely related to the ability of melanin production and that the possible existence of a unique isoenzyme may reflect the intensity of tumorigenic and/or metastasis.