GAMMA-GLUTAMYL-TRANSFERASE TRANSPEPTIDASE, TYROSINASE, AND 5-S-CYSTEINYLDOPA PRODUCTION IN MELANOMA-CELLS

[摘要] The distribution of .gamma.-glutamyl transpeptidase (.gamma.-GTP), tyrosinase and 5-S-cysteinyldopa (5-S-CD) within melanoma cells was studied in vitro and in vivo. Sodium periodate treatment of intact [mouse] B-16 melanoma cells inhibits .gamma.-GTP present as an ectoenzyme. These periodate-treated cells in the presence of 10-5 M dopa and glutathione continued to secrete large quantities of 5-S-CD in their medium. The large-granule fraction of Greene''s melanotic melanoma contains substantial amounts of both tyrosinase and .gamma.-GTP. Further separation of the large-granule fraction into sub-fractions indicates that tyrosinase and .gamma.-GTP seem to co-exist with premelanosome. Glutathione-dependent 5-S-CD genesis possibly proceeds within premelanosomes through the formation of glutathione-dopa. The excess of glutathione-dopa and 5-S-CD, unutilized for pheomelanin formation, overflow into the cytoplasm.