Tyrosinase hamster melanoma

Figure 12, Variation in lag time for tyrosine hy-droxylation hy hamster melanoma tyrosinase, (A) no DOPA (B) 4 X (C) 8 X (D) 1,6...

Catechol as an Activator of Tyrosinase. The phenolase activity of tyrosinase has been studied less completely than the catecholase activity, partly because of the lack of a satisfactory assay procedure. The phenolase reaction, however, is characterized by a lag time which can be abolished by adding dihydroxyphenylalanine (DOPA), the immediate product of the hydroxylation reaction 29S4, 102, 117), This phenomenon has been described by several investigators (29-34) and is illustrated in Figure 12, from Pomerantz and Warner (117), using the enzyme from Hamster melanoma. The same phenomenon has been analyzed by Duckworth and Coleman (102) for the mushroom enzyme. In the absence of DOPA, maximum velocity of the hydroxylase reaction is not reached for several minutes. Pomerantz and Warner (117) devised a convenient assay for the phenolase reaction by determining the radio-... 

P8. Pomerantz, 8. H., Separation, purification, and properties of two tyrosinases from hamster melanoma. J. Biol. Chem. 238, 2351-2357 (1963). 

Slominski A, Costantino R (1991) Molecular Mechanism of Tyrosinase Regulation by L-Dopa in Hamster Melanoma Cells. Life Sci 48 2075... 

However, when Syrian (golden) hamster melanoma cells were fused with non-melanin-producing C3H mouse cells [104], and the hybrid line was isolated by the appropriate selection, no melanin production was observed in the hybrid cells, nor were tyrosinase and dopa oxidase activities detected in their extracts [104]. The parental melanoma cells had the enzymic activities and produced pigment. Nevertheless, in the hybrid cells, which possessed the expected hybrid karyotype, the lactate and malate dehydrogenase isozyme patterns were combinations of both parental types [104]. Thus, one might conclude that in the non-melanin-producing C3H parental cells there existed a specific diffusible enzyme... 

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