The use of urea by Evernia prunastri thalli.

Thalli of Evernia prunastri floated on 40 mM urea synthesize urease (EC3.5.1.5) which is, in part, retained in the cells as well as secreted into the external medium. By using [(14)C]urea, it has been shown that the (14)CO2 evolved by the action of urease is mainly incorporated into phenolic compounds. Evernic acid has the highest radioactivity when incubations are carried out in the light. The orsellinate moiety of this molecule contains ten times more radioactivity than the everninic acid moiety. This could be explained by the assumption that orsellinic acid is the first product of cyclisation of the polyketide chain in the biosynthetic pathway.