© Frédérique Voisin-Demery
© Frédérique Voisin-Demery

German universities decode melanin

Using mutation of the tyrosinase enzyme, researchers at the German universities of Mainz and Kiel have revealed the molecular mechanics behind the synthesis of melanin.

The pigment melanin is ubiquitous in most species of life from humans, in which it determines hair and skin colour, to insects, in which it protects against pathogenic micro-organisms whilst helping to repair tissue damage, and in the dark spots on bananas, for example.

The formation of melanin was never fully understood, but researchers at Mainz and Kiel have now closed the information gap.

The enzyme tyrosinase is active at the core of the mechanism. The discovery of this allows the development of applications in the cosmetics and food industries, as well as in environmental technology and medicine.

Professor Dr Heinz Decker of the Institute of Molecular Biophysics at Johannes Gutenberg University (JGU), Mainz, said: “We previously did not fully understand the role played by this enzyme. In fact, we knew more about the activities of catechol oxidase, a related but less potent enzyme that is also involved in the synthesis of melanin.”

Decker, working alongside Even Solem, also of Mainz, and Professor Felix Tuczek of Kiel decided to experiment on the mechanism responsible for tyrosinase activity by isolating a catechol oxidase from Riesling wine leaves and converted it into a tyrosinase by means of a biotechnological process involving targeted mutation.

The researchers found that the difference in reactivity is attributable to two amino acids, a highly conserved glutamic acid and asparagine located near the catalytic centre, forming a bond with a specific water molecule within the protein matrix. This bond is strong enough to cause a charge displacement in the water molecule, making one side strongly negative. This then activates the tyrosinase.

Experts predict that systematic improvements in biotechnological medicine, cosmetics production and environmental research can now be developed as a result.

The study is available for download here.