Sequential induction of maltose-permease and maltase systems in Saccharomyces cerevisiae

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Abstract
The induction of maltose-permease and maltose systems was studied in stationary cells of 3 strains of S. cerevisiae. In strain 240 M maltose permease was induced 2.75-3.5 hours after adding the inducer. This synthesis was independent of the presence of an external N source. In the absence of exogenous N no detectable maltose was formed, but if N was present the maltose system was induced 3.2-3.5 hours after the addition of the inducer. When uninduced cells of strain 240 M were exposed to maltose for 3.5 hours or more in the absence of N and amino acids were then added, the maltose system was synthesized with little further lag over a period of about 20 minutes. Thus separate induction of transport and hydrolysing systems was possible in this strain. By contrast, in strains 366 and 239, induction of the maltose systems appeared to be independent of a supply of exogenous N. Indeed, in strain 366 it appeared also to be independent of preinduction of the transport system. Strain 239 possessed a marked ability to transfer C14 from [C14]maltose to [C14]trehalose at an external pH of 8.5 where yeast maltoses are usually inactive. Strain 366 also exhibited this ability to a much smaller degree.