New nitrosoureas and their spin-labeled derivatives influence dopa-oxidase activity of tyrosinase.
Tyrosinase is a key enzyme in melanine biosynthesis. The modulating effect of cytostatic agents on DOPA-oxidase activity of tyrosinase could be linked with the drug treatment of melanoma tumors. Two groups of nitrosoureas which influence DOPA-oxidase activity of tyrosinase were studied: new nitrosoureas and their spin-labeled derivatives synthesized in our laboratory. Using Burnett's spectrophotometric method (Burnett et al., 1967) the following effects were established: inhibition by CCNU, inhibition and the activating effects of the other investigated nitrosoureas depend on their physicochemical half-life. The predominant activating effect of the spin-labeled derivatives is due to the nitroxyl radical present in these compounds.
Rachkova
M
M
Department of Chemistry and Biochemistry, Medical Institute, Stara Zagora, Bulgaria.
Raikova
E
E
Raikov
Z
Z
D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology; D001487:Basidiomycota / Q000201:enzymology; D006801:Humans; D008130:Lomustine / Q000494:pharmacology; D008545:Melanoma / Q000188:drug therapy; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D009607:Nitrosourea Compounds / Q000737:chemistry / Q000494:pharmacology*; D013113:Spin Labels; D013329:Structure-Activity Relationship
D000970:Antineoplastic Agents; D009607:Nitrosourea Compounds; D013113:Spin Labels; D008130:Lomustine; D014442:Monophenol Monooxygenase