Abstract
Saccharomyces cerevisiae accumulates l-malic acid through a cytosolic pathway starting from pyruvic acid and involving the enzymes pyruvate carboxylase and malate dehydrogenase. In the present study, the role of malate dehydrogenase in the cytosolic pathway was studied. Overexpression of cytosolic malate dehydrogenase (MDH2) under either the strong inducible GAL10 or the constitutive PGK promoter causes a 6- to 16-fold increase in cytosolic MDH activity in growth and production media and up to 3.7-fold increase in l-malic acid accumulation in the production medium. The high apparent K m of MDH2 for l-malic acid (11.8 mM) indicates a low affinity of the enzyme for this acid, which is consistent with the cytosolic function of the enzyme and differs from the previously published K m of the mitochondrial enzyme (MDH1, 0.28 mM). Under conditions of MDH2 overexpression, pyruvate carboxylase appears to be a limiting factor, thus providing a system for further metabolic engineering of l-malic acid production. The overexpression of MDH2 activity also causes an elevation in the accumulation of fumaric acid and citric acid. Accumulation of fumaric acid is presumably caused by high intracellular l-malic acid concentrations and the activity of the cytosolic fumarase. The accumulation of citric acid may suggest the intriguing possibility that cytosolic l-malic acid is a direct precursor of citric acid in yeast.
Similar content being viewed by others
Author information
Authors and Affiliations
Additional information
Received: 22 January 1997 / Received revision: 14 April 1997 / Accepted: 19 April 1997
Rights and permissions
About this article
Cite this article
Pines, O., Shemesh, S., Battat, E. et al. Overexpression of cytosolic malate dehydrogenase (MDH2) causes overproduction of specific organic acids in Saccharomyces cerevisiae . Appl Microbiol Biotechnol 48, 248–255 (1997). https://doi.org/10.1007/s002530051046
Issue Date:
DOI: https://doi.org/10.1007/s002530051046