NDLI: Tyrosinase isoenzymes in mammalian melanocytes. 2. Differential activation by alpha-melanocyte-stimulating hormone

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Tyrosinase isoenzymes in mammalian melanocytes. 2. Differential activation by alpha-melanocyte-stimulating hormone

Content Provider	Scilit
Author	Valverde, Paloma Garcia-Borron, Jose C. Jimenez-Cervantes, Celia Solano, Francisco Lozano, Jose A.
Copyright Year	1993
Description	Journal: Journal of Biological Inorganic Chemistry In mouse melanoma melanocytes, α‐melanocyte‐stimulating hormone (MSH) stimulates differentiation, melanin synthesis and tyrosinase activity. However, the molecular mechanisms underlying these events have not yet been characterized. We have studied the activation of tyrosinase by MSH. Treatment of B16 melanoma cells with either theophylline, MSH, or its superpotent analog $[Ahx^{4}$, $DPhe^{7}$]MSH promotes a larger induction of tyrosine hydroxylase than of dopa oxidase activity in whole cell extracts. This higher activation of tyrosine hydroxylation was found not only in the melanosomal but also in the microsomal fraction; it appears to be dependent on continued transcription and translation since it can be blocked by actinomycin and cycloheximide. The tyrosinase activity of control and theophylline‐treated extracts displayed several kinetic differences, including different $K_{m}$ values for both substrates and requirements for the cofactor L‐dopa. SDS/PAGE, followed by a sensitive specific activity stain, demonstrated that melanosomes of control cells contain one lower‐electrophoretic‐mobility form of tyrosinase, whereas melanosomes of cells treated with either theophylline or MSH display, in addition to the lower‐mobility form, a faster‐migrating activity band. These tyrosinase forms are not interconvertible by proteolysis or deglycosylation. Their nature is discussed as related to the properties of the previously described low‐ and high‐electrophoretic‐mobility tyrosinases (LEMT and HEMT), as well as of the proteins encoded by the c and b loci.
Related Links	https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1993.tb18275.x
Ending Page	548
Page Count	8
Starting Page	541
ISSN	09498257
e-ISSN	14321327
DOI	10.1111/j.1432-1033.1993.tb18275.x
Journal	Journal of Biological Inorganic Chemistry
Issue Number	2
Volume Number	217
Language	English
Publisher	Wiley-Blackwell
Publisher Date	1993-10-01
Access Restriction	Open
Subject Keyword	Journal: Journal of Biological Inorganic Chemistry Biotechnology and Microbiology
Content Type	Text
Resource Type	Article
Subject	Biochemistry Inorganic Chemistry

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