How white mushrooms turn brown

An enzyme called tyrosinase, which is formed prior to fungal spoiling, is responsible for mushrooms turning brown, says a study that looked into the mechanisms behind the "browning reaction".

Understanding the mechanism of enzyme tyrosinase pigmentation is currently of both medical as well as technological interest.

Six different tyrosinases (PPO1 to 6) exist within the mushroom, two of which (PPO3 and PPO4) occur in larger quantities.

"This research has allowed for the crystallisation and three-dimensional structure of PPO4 to be resolved," said lead researcher Anette Rompel from the University of Vienna in Austria.

The enzyme responsible for the mechanism of food spoilage is formed within eukaryotes (organisms that have a nucleus) as an inactive precursor during the developmental phase of an organism, the study noted.

For the study, the researchers developed for the first time a method that allows for the stage one isolation of latent tyrosinase from their natural source.

The findings appeared in the journals Phytochemistry and Acta Crystallographica.