Regulation of Urea Production in Evernia prunastri: Effects of L-Arginine Metabolites

Abstract

Summary Cell-free extracts of Evernia prunastri thallus floated on 40 mM L-arginine exhibit enzyme activities for the following reactions: arginine hydrolysis, arginine decarboxylation and agmatine hydrolysis. L-arginine induces arginase (EC 3.5.3.1), L-arginine decarboxylase (EC 4.1.1.19) and agmatine amidinohydrolase (EC 3.5.3.11) whereas urea behaves as a catabolite repressor of arginase and agmatine amidinohydrolase. Urea may start the regulation process when, from L-arginine, a relatively low concentration of that compound accumulates in the thallus producing a feedback inhibition of these enzymes, as deduced from the study of its action on the purified proteins. Dry weight of samples drastically diminishes when putrescine is added to the media.