Isolation and characterization of a Golgi-rich fraction from the Harding-Passey mouse melanoma.

Km OF TYROSINASE IN MICROSOMES IS HIGHER THAN THAT IN MELANOSOMES

“…1.14.18.IJ, the enzyme responsible for melanin formation, is highly concentrated (I). However, tyrosinase activity has not only been found in melanosomes but al~o in smooth and rough surface membranes and Golgi apparatus isolated from Harding-Passey mouse melanomas (2). As these extra-melanosomal tyrosinases do not appear to produce melanin under physiological conditions, it is suspected that some regulatory mechanism(s) controling the activity of these enzymes may be present.…”

“…In animal melanocytes in uiuo, melanin formation occurs only in the melanosomes, despite the fact that tyrosinases exist in rough and smooth surface membranes and Golgi apparatus (2). On the other hand, it is well-known in electromicroscopic observations that melanin deposits increase not only on the melanosomes, but that new deposits also appear on the rough and smooth membranes and Golgi appearatus in the melanocytes, when biopsy specimens from skin or melanoma are incubated in vitro in a high concentration of tyrosine solution for a long time.…”

Electrophoretic Profile of Tyrosinase Treated With Neuraminidase in Various Subcellular Fractions From Mouse Melanoma*

“…and fucose appear to the attached to thyroglobulin and many other glycoproteins only within the Golgi apparatus (5,8). Although the purity of all these particles is to be carefully considered, it is assumed that, in melanocytes, tyrosinase, a kind of secretory protein, may be Fractions of melanosomes, Golgi apparatus, and smooth or rough surface membrane were prepared from Harding-Passey mouse melanoma by the method described previously (6). 1, the reduction in electrophoretic mobility of neuraminidase-treated tyrosinase in the rough and smooth surface membrane fractions appears to indicate that the sialic acid residue has already been added to the enzyme in the rough and smooth surface membranes before reaching the Golgi apparatus.…”

“…1, the reduction in electrophoretic mobility of neuraminidase-treated tyrosinase in the rough and smooth surface membrane fractions appears to indicate that the sialic acid residue has already been added to the enzyme in the rough and smooth surface membranes before reaching the Golgi apparatus. Although the purity of all these particles is to be carefully considered, it is assumed that, in melanocytes, tyrosinase, a kind of secretory protein, may be Fractions of melanosomes, Golgi apparatus, and smooth or rough surface membrane were prepared from Harding-Passey mouse melanoma by the method described previously (6). Neuraminidase from Clostridium perfringens was obtained from Sigma Chemical Company (St.…”