Evidence for regulatory trehalase activity in Candida utilis

Candida utilis cells constitutively contain an acetate-insensitive intracellular trehalase (α,α-trehalose glycohydrolase; EC 3.2.1.28) whose activity is maximal during exponential growth. Cells grown on glucose, sucrose, or ethanol as carbon source show decreased levels of this trehalase activity as the cultures enter the stationary phase. The enzyme activity from stationary phase cells can be restored to the levels present in growing cells by preincubation of the cell extracts with adenosine 3′,5′-cyclic monophosphate and adenosine 5′-triphosphate. In vitro activation is also accomplished by addition of the catalytic subunit of a protein kinase preparation and adenosine 5′-triphosphate. The enzyme activity is enhanced in vivo by the presence of glucose or fluoride. Treatment of the trehalase with phosphatase results in a substantial loss of trehalase activity. Both activated and nonactivated trehalases show similar properties (Km = 1.01 × 10−2 M) and seem to be due to an enzyme with a molecular weight of 280 000. The data obtained are consistent with a regulatory model involving phosphorylation and dephosphorylation of the enzyme to control trehalase activity. In addition, another trehalase is present in this yeast whose activity is markedly inhibited by acetate.