Antonio Rescigno

Principal areas of expertise: Chemistry of Antioxidants, Quinones, and Related Enzymes; Structure and Function of the Enzymes Involved in Browning Reactions; Enzyme Purification, Properties and Biotechnological Applications of Immobilised Enzymes and their Emulators

♦ Getting dark, but not too dark!

The main topics of our research center on some aspects of melanic pigment formation in both animal and plant cells, and also in fungi. Principal topics focused on enzymatic implications in this occurrence and include the use of tyrosinase enzyme as a model study.

Browning in plants, fruits, vegetables and mushrooms. Enzymatic and non-enzymatic browning reactions cause deterioration of food during storage and processing. Several enzymes are responsible for browning phenomenon. Phenylalanine ammonia-lyase (PAL), polyhenol oxidase (PPO), peroxidase (POD) activities lead to the formation and accumulation of brown phenolic compounds. An especial attention is given to PPO and PPO-catalyzed oxidation of phenolics to quinones which then polymerize to dark melanin pigments of non-well known structure in textiles.

Pigmentation of mammalian skin. Melanin is synthesized enzymatically from tyrosine within melanosomes. Tyrosinase, a copper enzyme belonging to type-3 copper proteins, is involved in the initial step of melanin biosynthesis and it is widespread throughout microrganisms, plant and fungal species, invertebrates, and vertebrates. This enzyme catalyses the o-hydroxylation of monophenols to the corresponding catechols (monophenolase or cresolase activity) and the oxidation of such catechols to the corresponding o-quinones (diphenolase or catecholase activity).