CONTROL OF YEAST NEUTRAL TREHALASE BY DISTINCT POLYPHOSPHATES AND RIBONUCLEIC-ACID

The activity of yeast trehalase when assayed at pH 7 in a crude extract was found to increse 2- to 3-fold upon incubation with 0.1% (v/v) polyethyleneimine or other polycations such as polylysine (0.075-mMol) and calf thymus histones (0.08 mMol). Incubation with 3 mM-Mn2+ and 5 mM-Ca2+ also led to 3- and 1.6-fold increases in trehalase activity, respectively. The activities of 11 other enzymes assayed in the crude yeast extract did not increase after addition of polyethylene imine. At concentrations of polyethylenemine that maximally stimulated trehalase activity, 97% of the total RNA present in the crude extract, 40% of total protein, and 60% of the polyphosphate (assayed as inorganic phosphate liberated during 7 min incubation at 95.degree. C and pH O) were found to be precipitated. A similar finding was made with trehalase-stimulating concentrations of Mn2+. Activation of trehalase by polyethylene imine rendered this enzyme susceptible to inhibition by a preparation of total yeast RNA, inorganic polyphosphates, and related polyanions. We present further evidence that the removal of a distinct RNA and/or polyphosphate is the basic principle of polyethyleneimine-induced activation of trehalase. A more pronounced stimulation of trehalase activity (4-fold) could be obtained by enzymatic phosphorylation with ATP in the presence of cyclic AMP and Mg2+ as described by van Soligen and van der Plaat (1975) [9]. Thus, trehalase 2-fold activated by polyethylene imine was further activated by another 2-fold increase by enzymatic phosphorylation. Conversely, no additional stimulation by polyethylene imine was obtained for the maximally active, phosphorylated enzyme. We conclude that phosphorylation-mediated activation of trehalase is a two-step event, one being the removal of an inhibitor, which can be achieved by polyethylene imine or related cations independent on phosphorylation. The most likely candidate for the inhibitor appears to be a distinct RNA.