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TYROSINASE AND γ ‐GLUTAMYL TRANSPEPTIDASE IN 5‐S‐CYSTEINYLDOPA GENESIS WITHIN MELANOTIC AND AMELANOTIC MELANOMAS
Author(s) -
Mojamdar Manoj,
Ichihashi Masamitsu,
Mishima Yutaka
Publication year - 1982
Publication title -
the journal of dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 65
eISSN - 1346-8138
pISSN - 0385-2407
DOI - 10.1111/j.1346-8138.1982.tb02605.x
Subject(s) - tyrosinase , gtp' , melanoma , in vitro , in vivo , amelanotic melanoma , chemistry , cysteine , biochemistry , glutathione , enzyme , iodoacetamide , melanosome , microbiology and biotechnology , biology , melanin , cancer research
The roles of tyrosinase and γ ‐glutamyl transpeptidase ( γ ‐GTP) in 5‐S‐cysteinyldopa (5‐S‐CD) genesis in melanotic and amelanotic melanoma cells has been investigated in vitro and in vivo . Complete inhibition of tyrosinase by 10 –3 M diethyl dithiocarbamate has been found to partially inhibit dopa‐cysteine dependent 5‐S‐CD genesis by cultured melanoma cells. On the other hand iodoacetamide, an inhibitor of γ ‐GTP, has been found to completely inhibit dopa‐glutathione dependent 5‐S‐CD genesis by these cells. Melanotic melanoma has been found to be rich in tyrosinase and γ ‐GTP activity. In contrast, the amelanotic melanoma studied here was found to lack tyrosinase activity and to have very little γ ‐GTP activity. The sub‐cellular distribution of these enzymes in melanotic melanoma cells has revealed that while the melanosome‐rich fraction is high in tyrosinase activity, it contains no substantial γ ‐GTP activity. These findings indicate that 5‐S‐CD can form non‐enzymically in vitro from dopa and cysteine. Further, it also provides evidence that γ ‐GTP is the enzyme that converts glutathione‐dopa to 5‐S‐CD within melanoma cells.