Transport of lactate and other short-chain monocarboxylates in the yeast Saccharomyces cerevisiae

Abstract

Saccharomyces cerevisiae IGC4072 grown in lactic acid medium transported lactate by an accumulative electroneutral proton-lactate symport with a proton-lactate stoichiometry of 1:1. The accumulation ratio measured with propionate increased with decreasing pH from ca. 24-fold at pH 6.0 to ca. 1,400-fold at pH 3.0. The symport accepted the following monocarboxylates (Km values at 25 degrees C and pH 5.5): D-lactate (0.13 mM), L-lactate (0.13 mM), pyruvate (0.34 mM), propionate (0.09 mM), and acetate (0.05 mM), whereas apparently a different proton symport accepted formate (0.13 mM). The lactate system was inducible and was subject to glucose repression. Undissociated lactic acid entered the cells by simple diffusion. The permeability of the plasma membrane for undissociated lactic acid increased exponentially with pH, and the diffusion constant increased 40-fold when the pH was increased from 3.0 to 6.0.

Evidence for rapid uptake of d‐galacturonic acid in the yeast Saccharomyces cerevisiae by a channel‐type transport system

“…The uptake of D-galacturonic acid was strongly enhanced at low pH, which might have been an indication for symport. However, there was only modest inhibition by the protonophores DNP and CCCP, which in the literature have been shown to inhibit symport systems completely at even lower concentrations [14,15]. In addition, we did not observe intracellular concentration of D-galacturonic acid above the extracellular substrate levels, nor a low K mvalue as has been reported previously for classical symport systems [25,26].…”

The putative monocarboxylate permeases of the yeast Saccharomyces cerevisiae do not transport monocarboxylic acids across the plasma membrane

“…However, X-gal overlay assays with cells incubated in the presence of other carbon sources (2% pyruvate, acetate, succinate and 0.1% oleic acid) did not reveal any differences in comparison to the wild-type (data not shown). Thus, none of the MCH genes is repressed by glucose or is completely dependent on the presence of lactic acid, in contrast to the reported monocarboxylate transport systems of S. cerevisiae (Cá ssio et al, 1987;Casal et al, 1995Casal et al, , 1996.…”

“…The mechanisms of transport of monocarboxylic acids in S. cerevisiae have already been described for the strains IGC 4072 (Cá ssio et al, 1987;Casal et al, 1996) and W303 (Casal et al, 1995). It was also previously shown that the product of JEN1 is a permease for monocarboxylates, inducible by lactic acid .…”

“…Transport across the plasma membrane is the first step in the metabolism of these substrates. Two different uptake systems for monocarboxylic acids have been described in S. cerevisiae: one which is shared by acetate, propionate and formate, and another which transports lactate, pyruvate, acetate and propionate (Cá ssio et al, 1987;Casal et al, 1995Casal et al, , 1996. The first system is constitutively expressed in cells growing on non-fermentable carbon sources, while the lactate transporter is specifically induced in cells grown in lactic acid medium.…”

Transport of acetate in mutants of Saccharomyces cerevisiae defective in monocarboxylate permeases

“…The transport of monocarboxylic acids through the plasma membrane, the ¢rst step of their metabolism, has been elucidated in the strain Saccharomyces cerevisiae IGC 4072 [1,2]. Two distinct monocarboxylate carriers were found, regarding either their speci¢city or regulation.…”