Assays for mammalian tyrosinase: a comparative study
Abstract
This work describes a comparative study of the tyrosinase activity determined using three methods which are the most extensively employed; two radiometric assays using L-tyrosine as substrate (tyrosine hydroxylase and melanin formation activities) and one spectrophotometric assay using L-dopa (dopa oxidase activity). The three methods were simultaneously employed to measure the activities of the soluble, melanosomal, and microsomal tyrosinase isozymes from Harding-Passey mouse melanoma through their purification processes. The aim of this study was to find any correlation among the tyrosinase activities measured by the three different assays and to determine whether that correlation varied with the isozyme and its degree of purification. The results show that mammalian tyrosinase has a greater turnover number for L-dopa than for L-tyrosine. Thus, enzyme activity, expressed as mumol of substrate transformed per min, is higher in assays using L-dopa as substrate than those using L-tyrosine. Moreover, the percentage of hydroxylated L-tyrosine that is converted into melanin is low and is affected by several factors, apparently decreasing the tyrosinase activity measured by the melanin formation assay. Bearing these considerations in mind, average interassay factors are proposed. Their values are 10 to transform melanin formation into tyrosine hydroxylase activity, 100 to transform tyrosine hydroxylase intomore »
- Authors:
- Publication Date:
- Research Org.:
- Universidad de Murcia (Spain)
- OSTI Identifier:
- 5905058
- Resource Type:
- Journal Article
- Journal Name:
- Pigment Cell Res.; (United States)
- Additional Journal Information:
- Journal Volume: 1:5
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 59 BASIC BIOLOGICAL SCIENCES; MELANIN; BIOSYNTHESIS; TYROSINASE; ENZYME ACTIVITY; COMPARATIVE EVALUATIONS; EXPERIMENTAL NEOPLASMS; FRACTIONATION; ISOENZYMES; ISOTOPE DILUTION; MELANOMAS; MICE; MICROSOMES; OXIDOREDUCTASES; RADIOASSAY; SPECTROPHOTOMETRY; TYROSINE; AMINO ACIDS; ANIMALS; CARBOXYLIC ACIDS; CELL CONSTITUENTS; DISEASES; ENZYMES; HYDROXY ACIDS; HYDROXY COMPOUNDS; HYDROXYLASES; ISOTOPE APPLICATIONS; MAMMALS; NEOPLASMS; ORGANIC ACIDS; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; ORGANOIDS; PIGMENTS; RODENTS; SEPARATION PROCESSES; SYNTHESIS; TRACER TECHNIQUES; VERTEBRATES; 550201* - Biochemistry- Tracer Techniques
Citation Formats
Jara, J R, Solano, F, and Lozano, J A. Assays for mammalian tyrosinase: a comparative study. United States: N. p., 1988.
Web. doi:10.1111/j.1600-0749.1988.tb00128.x.
Jara, J R, Solano, F, & Lozano, J A. Assays for mammalian tyrosinase: a comparative study. United States. https://doi.org/10.1111/j.1600-0749.1988.tb00128.x
Jara, J R, Solano, F, and Lozano, J A. 1988.
"Assays for mammalian tyrosinase: a comparative study". United States. https://doi.org/10.1111/j.1600-0749.1988.tb00128.x.
@article{osti_5905058,
title = {Assays for mammalian tyrosinase: a comparative study},
author = {Jara, J R and Solano, F and Lozano, J A},
abstractNote = {This work describes a comparative study of the tyrosinase activity determined using three methods which are the most extensively employed; two radiometric assays using L-tyrosine as substrate (tyrosine hydroxylase and melanin formation activities) and one spectrophotometric assay using L-dopa (dopa oxidase activity). The three methods were simultaneously employed to measure the activities of the soluble, melanosomal, and microsomal tyrosinase isozymes from Harding-Passey mouse melanoma through their purification processes. The aim of this study was to find any correlation among the tyrosinase activities measured by the three different assays and to determine whether that correlation varied with the isozyme and its degree of purification. The results show that mammalian tyrosinase has a greater turnover number for L-dopa than for L-tyrosine. Thus, enzyme activity, expressed as mumol of substrate transformed per min, is higher in assays using L-dopa as substrate than those using L-tyrosine. Moreover, the percentage of hydroxylated L-tyrosine that is converted into melanin is low and is affected by several factors, apparently decreasing the tyrosinase activity measured by the melanin formation assay. Bearing these considerations in mind, average interassay factors are proposed. Their values are 10 to transform melanin formation into tyrosine hydroxylase activity, 100 to transform tyrosine hydroxylase into dopa oxidase activity, and 1,000 to transform melanin formation into dopa oxidase activity. Variations in these values due to the presence in the tyrosinase preparations of either inhibitors or regulatory factors in melanogenesis independent of tyrosinase are also discussed.},
doi = {10.1111/j.1600-0749.1988.tb00128.x},
url = {https://www.osti.gov/biblio/5905058},
journal = {Pigment Cell Res.; (United States)},
number = ,
volume = 1:5,
place = {United States},
year = {Fri Jan 01 00:00:00 EST 1988},
month = {Fri Jan 01 00:00:00 EST 1988}
}