POSSIBLE ROLE OF ISOASPARTYL METHYLTRANSFERASE TOWARDS REGULATION OF ACID TREHALASE ACTIVITY IN SACCHAROMYCES-CEREVISIAE

Logarithmically growing cells of S. cerevisiae contained high neutral trehalase (NT) activity while stationary-phase cells had high acid tre halase (AT) activity. Change in activity profile of AT and NT were dif ferent during growth under different conditions, particularly during g rowth in acetate medium and up to 1 h of germination period, but that for AT and isoaspartyl methyltransferase (IMT) were found to be almost identical. Concomitant increase in NT activity as well as increase in cAMP level was noticed at the onset of spore germination. Increase in AT and IMT activities as well as decrease in S-adenosyl-L-methionine (AdoMet) level were noticed during stationary phase of growth. Acidic polyacrylamide gel electrophoresis and subsequent autoradiography reve aled that substrate of IMT was a protein of molar mass around 82 kDa w hich could be an AT. Methylated AT was found to be more active while n on-methylated AT was relatively less active in comparison to the untre ated sample. Since AT existed as an equilibrium mixture of protomer an d oligomer, it was suggested that IMT catalysed carboxyl methylation m ight have some contribution towards the regulation of AT activity.