Synthesis of 1,3-β-Glucanases in Saccharomyces cerevisiae During the Mitotic Cycle, Mating, and Sporulation

Abstract

Upon fractionating Saccharomyces cerevisiae asynchronous cultures by sucrose density gradient centrifugation in a zonal rotor and examining the exo-1,3-β-glucanase and deoxyribonucleic acid content of the cells, a periodic step increase in the activity of this enzyme was observed, indicating a discontinuous pattern of synthesis or activation of exo-1,3-β-glucanase during the mitotic cycle at the transition from the S to the G 2 phase. Similar results were obtained for endo-1,3-β-glucanase by assaying activity against oxidized laminarin in permeabilized cells, suggesting that the synthesis of endo-1,3-β-glucanase is controlled in the same way. When a and α strains were mated, the specific activity of cell extracts against laminarin, oxidized laminarin, and pustulan remained constant while zygote formation was taking place. However, when growth resumed, active synthesis of 1,3-β-glucanases took place as shown by the occurrence of a significant increase in the specific activity against the three substrates. Specific changes in the level of glucan degradative enzymes, not observed in a haploid parental strain, occurred when the diploid S. cerevisiae AP-1 was induced to sporulate. The sporulation process triggered the activation of first the pustulan degradative capacity and then the capacity to hydrolyze oxidized laminarin. The specific activity against this substrate was 10 times higher than that against pustulan.