Regulation of Isoamyl Alcohol Formation via Ehrlich Pathwas in Saccharomyces cerevisiae

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The regulation mechanism of iAmOH formation restricted to the Ehrlich pathway was studied using a leucine-requiring mutant (lue2) of Saccharomyces cerevisiae which could form the higher alcohol only from leucine.When leucine was the sole nitrogen source, the amount of iAmOH increased with an increase of luecine concentraiton to reach a saturation level (8 mmoles/l) of iAmOH formation at 10 mM leucine. Addition of ammonium sulfate lowered the saturation level to about a half. Neither isoleucine nor ammonium sulfate reduced the yield of iAmOH as long as the leucine concentration was low, but addition of both isoleucine and ammonium sulfate inhibited iAmOH formation to a great extent (a fifth) at any low concentration of leucine. The effect of valine was quite similar to that of isoleucine, whereas glutamic acid was different from ammonium sulfated in the mode of inhibition. The rate of iAmOH formation at the initial stage of fermentation was retarded by isoleucine if the leucine concentraiton was lower than 6 mM, but was extremely raised if the leucine concentration was high. A tracer experiment with ^<14>C-leucine revealed three kinds of regulation of iAmOH formation;(1)inhibition related to retarded uptake of leucine, (2)inhibition related to raised incorporation of leucine into cellular components, and (3)inhibition related to cessation of leucine uptake. The latter appeared when the nitrogen source was a mixture of leucine, isoleucine, and ammonium sulfate, and the leucine uptake ceased at 24 hr of fermentation while 50% of the input leucine still remained.In addition, since 35% was incorporated into cellular components, (i.e. the second kind of regulation), only 15% was converted to iAmOH in the medium containing the nitrogen source mixture mentioned above.
社団法人日本生物工学会の論文
1980-08-25

Regulation of Isoamyl Alcohol Formation via Ehrlich Pathwas in Saccharomyces cerevisiae

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