Polüfenooloksidoos

Polüfenooloksidoos, commonly known as polyphenol oxidase (PPO), is an enzyme widely distributed in plants, fungi, and some bacteria. It plays a crucial role in various biochemical processes, particularly in the synthesis of melanin and the browning reactions observed in cut fruits and vegetables. PPO belongs to the group of copper-containing oxidoreductases, which utilize oxygen to catalyze the oxidation of phenolic compounds.

The primary function of polyphenol oxidase involves the hydroxylation of monophenols to o-diphenols, followed by the oxidation of these diphenols to o-quinones. These quinones are highly reactive and can undergo further polymerization, leading to the formation of melanin pigments or other brown-colored compounds. This enzymatic activity is responsible for the undesirable browning in foods like apples, potatoes, and mushrooms, which can affect their appearance and nutritional quality.

PPO is found in various plant tissues, including leaves, stems, roots, and fruits. Its presence is particularly notable in the epidermal and subepidermal layers of plant organs. The enzyme is synthesized as an inactive precursor, which is activated upon tissue damage or disruption of cellular integrity. This activation triggers the browning reaction, making PPO a significant factor in post-harvest food spoilage.

In addition to its role in plant physiology, PPO has been studied for its potential applications in biotechnology and medicine. For instance, it is used in the production of melanin-based pigments for dyes and cosmetics. However, its activity can also be harnessed to develop strategies for preserving fresh produce by inhibiting the enzyme through physical, chemical, or enzymatic means. Research continues to explore the diverse functions and potential uses of polyphenol oxidase in both natural and industrial contexts.