A Fungal Membrane-Associated Phosphoenolpyruvate: glucose Phosphotransferase System, which Includes Adenylyl Cyclase, in the Lichen Evernia prunastri

Abstract

Summary The lichen Evernia prunastri is capable of accumulating glucose from liquid media by passive diffusion as well as by active uptake and phosphorylation of the sugar. This latter mechanism of glucose uptake is inhibited by cyclic AMP whose levels, in turn, are inhibited by glucose in lichen cells. An enzyme complex that phosphorylates glucose using phosphoenolpyruvate as a phosphate donor has been purified 2770-fold from lichen membranes. This enzyme complex, which is composed of five distinct subunits, has a molecular mass of about 100 kDa. The enzyme uses glucose preferentially, but can also use fructose as a substrate. Phosphoenolpyruvate, but not ATP, serves as a phosphate donor. The enzyme contains adenylyl cyclase as a constitutive subunit and is completeley restricted to the fungal partner of the lichen thallus.