Biochemical characterization of neutral trehalase activity in Saccharomyces boulardii

Lyophilized cells of the non-pathogenic yeast Saccharomyces boulardii are u sed in many countries for the treatment of several types of diarrhoea and o ther gastrointestinal diseases. Although the cells must be viable, their me chanism of action is unknown. The disaccharide trehalose is a protectant ag ainst several forms of environmental stress in yeast and is involved in mai ntaining cell viability. There is no information on the enzymes involved in degradation of trehalose in S. boulardii. The aim of the present study was to characterize trehalase activity in this yeast. Cells of S. boulardii gr own in glucose exhibited neutral trehalase activity only in the exponential phase. Acidic trehalase was not detected in glucose medium. Cells grown in trehalose exhibited acid and neutral trehalase activities at all growth st ages, particularly in the exponential phase. The optimum pH and temperature values for neutral trehalase activity were determined as 6.5 and 30 degree sC respectively, the half-life being approximately 3 min at 45 degreesC. Th e relative molecular mass of neutral trehalase is 80 kDa and the K 6.4 mM ( +/-0.6). Neutral trehalase activity at pH 6.5 was weakly inhibited by 5 mM EDTA and strongly inhibited by ATP, as well as the divalent ions Cu++, Fe+ and Zn++. Enzyme activity was stimulated by Mg++ and Ca++ only in the abse nce of cAMP. The presence of cAMP with no ion additions increased activity by 40%.