Regulation of trehalose metabolism by protein methylation in a mutant strain of Saccharomyces cerevisiae

Abstract

Trechaloseis a non reducing disaccharide occurring in a wide range of organisms, from bacteria, yeast, to lower and higher plants and insects. It is economically important as a potent stress protectant, protein and biological membrane stabilizer: hence biosynthesis of trchalose is an extremely important event. Regulation of trehalose metabolism by protein methylation has been reported from previous works of this laboratory. Trehalose metabolism was monitored during different stages of growth of Saccharomyces cerevisiae. HPLC and enzymatic determination of trehalose. glucose, trehalose 6 phosphate phosphatase TPP) and trehalose 6 phosphate synthase (TPS) were carried out. It was noticed that trchalose, glucose TPP and TPS pcaked at Aso20 during growth but during this period the hydrolyzing enzymes, acid trehalase (AT) and neutral trehalase (NT) are found to be low. Effect of a potent universal methyl group donor S-adenosyl-L-methionine (AdoMet), and a methylation inhibitor, oxidized adenosine (Adox) on trehalose metabolism has been studied. Trehalose metabolism is altered when YPD grown cells were incubated for I hr in presence of cither 1 mM Adox or AdoMet at 30'C and pH 6.0 TPS showed a slight increase in specific activity in cells incubated with AdoMet over Adox. Trehalose level of Adox treated cells were seen to be lower than control throughout the period of incubation. Trehalose level initially decreased upto 4 hours in all the sets by utilizing pre-synthesized trehalose, thereafter the AdoMet incubated cells showed sharp increase in trehalose content, in 8 hours 3 fold, in 24 hours nearly 5 fold with respect to others. At the point of 48 hours, cells reached stationary phase in all sets and trehalose level was found to increase.