[Different faces of phenoloxidase in animals]

Area of Science:

• Biochemistry
• Enzymology
• Immunology

Background:

• Phenoloxidases are oxidoreductases that oxidize phenols, with tyrosinase, catechol oxidase, and laccase often grouped under this term.
• Tyrosinase possesses both oxygenase and oxidase activities, crucial for melanin synthesis.
• Melanin, produced via tyrosinase, serves protective roles in humans (UV radiation) and invertebrates (cuticle hardening, immunity).

Purpose of the Study:

• To clarify the distinct roles and activities of phenoloxidase enzymes, particularly tyrosinase.
• To highlight the significance of tyrosinase in melanogenesis and its diverse functions.
• To explain the activation and immune relevance of the invertebrate phenoloxidase system.

Main Methods:

• Literature review and enzyme classification.
• Analysis of tyrosinase's dual enzymatic activities.
• Examination of melanin's physiological roles across species.

Main Results:

• Tyrosinase is uniquely capable of hydroxylating monophenols and oxidizing ortho-diphenols.
• Melanin formation by tyrosinase is essential for pigmentation and various physiological processes.
• In invertebrates, tyrosinase is activated via a serine protease cascade, forming the phenoloxidase system.

Conclusions:

• Tyrosinase is a pivotal enzyme in melanogenesis with varied biological functions.
• The invertebrate phenoloxidase system is integral to innate immunity and physiological processes like wound healing.