Tyrosinase scavenges tyrosyl radical

Area of Science:

• Biochemistry
• Enzymology
• Free Radical Chemistry

Background:

• Tyrosyl radicals are generated by UV irradiation of tyrosine.
• Melanosomes and tyrosinase enzyme are known to interact with tyrosine radicals.

Purpose of the Study:

• To elucidate the mechanism by which mushroom tyrosinase interacts with and scavenges tyrosyl radicals.
• To understand the role of the oxytyrosinase form in radical scavenging and enzyme activity.

Main Methods:

• Generating tyrosyl radicals using horseradish peroxidase and hydrogen peroxide.
• Analyzing the reaction kinetics of mushroom tyrosinase with tyrosyl radicals.
• Monitoring tyrosine, dityrosine, DOPAchrome, and oxygen production.

Main Results:

• Mushroom tyrosinase scavenged tyrosyl radicals in a dose-dependent manner.
• Oxytyrosinase reduced tyrosyl radicals to tyrosine, forming a met-form.
• The met-form of tyrosinase reacted with hydrogen peroxide to regenerate the active oxy-form, suppressing dityrosine formation and maintaining tyrosine levels.

Conclusions:

• Mushroom tyrosinase effectively scavenges tyrosyl radicals via a redox mechanism involving its oxy-form.
• This radical scavenging activity protects tyrosine from oxidation and maintains enzyme functionality.
• The findings provide insight into the protective roles of tyrosinase against oxidative stress.