Multiple forms of tyrosinase in rodents and lagomorphs with special reference to their genetic control in mice
✍ Scribed by Holstein, Thomas J. ;Quevedo, Walter C. ;Burnett, Jean B.
- Publisher
- John Wiley and Sons
- Year
- 1971
- Tongue
- English
- Weight
- 783 KB
- Volume
- 177
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
Polyacrylamide gel electropherograms of extracts of pigmented hair bulbs from rodents and lagomorphs indicate that tyrosinase exists in multiple molecular forms. Allelic substitutions at the a, b, c, d, and p color loci in mice reveal that the multiple forms of tyrosinase are subject to complex genetic influences. Depending upon genic constitution, a maximum of three electrophoretically-separable forms of tyrosinase (T1 = 80,000 m.w.; Tz = 62,000 m.w.; T3 = 66,000 m.w.) can be visualized by incubation of the polyacrylamide gels in GDOPA. In certain genotypes of mice, Tx, Tz, and T3 are either greatly reduced in activity or absent. Urea, SDS, and EDTA fail to dissociate tyrosinase suggesting that the multiple molecular forms of tyrosinase are not simple aggregates of monomeric subunits stabilized by non-covalent bonds.
Tyrosinase corresponding in mobility to the T1 of mice is also found in hair bulb extracts from black rats, black rabbits, gerbils and golden Syrian hamsters. The Tz and T3 components are distinct in the black rat but are represented by a single "Tz-T3" band in the gerbil, hamster and rabbit. An additional TO band is found in the black rat. Available evidence suggests that T1 of comparable electrophoretic mobility is widely distributed in mammals and may be an additional indication of an underlying broad homology of pigmentary genes. At present, it is not certain whether the multiple forms of tyrosinase are "true" isozymes or a single enzymic moiety bound to structural components of the melanosomal matrix. 1 Dedicated to the memory of Professor J. Walter Wilson, eminent research scientist, teacher and administrator. This investigation was supported by PHS Research grants CA-08292 and Ca-06097 from the National Cancer Institute, and PHS Training grants GM-00582 and HD-00019.
2 Throughout this paper the term "multiple molecular forms of tyrosinase" is used operationally to designate bands of tyrosinase activity within polyacrylamide gels and without specific reference to the possible underlying structure of the enzyme. In addition, the activity of tyrosinase reported here relates specifically to the second of its catalytic functions (DOPAoxidation), the f i s t being the oxidation of tyrosine to DOPA.