Characterization of proteinase A excretion from Saccharomyces cerevisiae in high sugar stress conditions

High sugar concentration culturing was commonly used in modern fermentation industry. However, it leads to the reduction of the foam stability in beer brewing due to the excess secretion of proteinase A. To better understand the characterization of proteinase A excretion from Saccharomyces cerevisiae in high sugar stress conditions, the cultures were grown by using YNB medium with a high concentration of glucose. Pro-PrA isolated from the medium was purified by gel exclusion chromatography, and the PrA activity was detected using fluorescent substrate analysis. The relative molecular weight of the purified PrA and pro-PrA was estimated at 42 and 54 kDa, respectively, by SDS-PAGE. It indicated that the metabolic behavior of PrA in the high glucose culturing was quite different from the normal conditions, and glucose concentration may have a big influence on its secreted process. Further study showed that PrA was released at the logarithmic growth phase of the culturing, and the amount of PrA was 11 times higher compared with the normal culturing. PrA was considered to be activated by itself under acidic conditions. And it was also confirmed in this work that the step-wise pathway for the autoactivation known as a pseudo-PrA has a major contribution to the autoactivation process of PrA zymogen outside the cell.