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Effect of Thiamine on Ethanol and Pyruvate Production in Helminthosporium maydis^1,2

Michael O. Garraway^b,c

^a Department of Botany, The Ohio State University, Columbus, Ohio 43210, ^b Department of Plant Pathology, The Ohio State University, Columbus, Ohio 43210, ^c The Ohio Agricultural Research and Development Center, Wooster, Ohio 44691

Growth of the fungus Helminthosporium maydis race T in a basal glucose-L-asparagine liquid medium, pH 5, is inhibited by thiamine-HCl. Analysis of the media for organic acids reveals that the extracellular pyruvate concentration decreases as the thiamine-HCl concentration of the medium increases. Extracellular ethanol, in contrast to pyruvate, increases in concentration as the thiamine-HCl concentration of the medium increases under both aerobic and anaerobic conditions.

The changes in ethanol and pyruvate levels in the presence of thiamine-HCl occur via a thiamine-mediated increase in the activity of pyruvate decarboxylase but not alcohol dehydrogenase. This increase in pyruvate decarboxylase activity appears to be due to an increase in the quantity of enzyme present rather than an activation of pre-existing enzyme. Whereas thiamine-pyrophosphate stimulates pyruvate decarboxylase activity in vitro, thiamine-HCl has no effect. Neither thiamine derivative affects alcohol dehydrogenase activity. The increase in pyruvate decarboxylase activity which accompanies an increase in the thiamine-HCl concentration of the medium is correlated with a decrease in the level of intracellular pyruvate.

¹ This research was supported in part by a United States Department of Agriculture Cooperative State Research Service grant, Contract No. 215-15-38, to The Ohio Agricultural Research and Development Center.

² A portion of this report is taken from a dissertation submitted by R.C.E. in partial fulfillment of the requirements for the Ph.D. degree in Botany at The Ohio State University.