title: Respiration-dependent utilization of sugars in yeasts: a determinant role for sugar transporters.
abstract: In many yeast species, including Kluyveromyces lactis, growth on certain sugars (such as galactose, raffinose, and maltose) occurs only under respiratory conditions. If respiration is blocked by inhibitors, mutation, or anaerobiosis, growth does not take place. This apparent dependence on respiration for the utilization of certain sugars has often been suspected to be associated with the mechanism of the sugar uptake step. We hypothesized that in many yeast species, the permease activities for these sugars are not sufficient to ensure the high substrate flow that is necessary for fermentative growth. By introducing additional sugar permease genes, we have obtained K. lactis strains that were capable of growing on galactose and raffinose in the absence of respiration. High dosages of both the permease and maltase genes were indeed necessary for K. lactis cells to grow on maltose in the absence of respiration. These results strongly suggest that the sugar uptake step is the major bottleneck in the fermentative assimilation of certain sugars in K. lactis and probably in many other yeasts.
authors.affiliation: Istituto di Genetica, Università degli Studi di Parma, Parma, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Goffrini
authors.forename: Iliana
authors.initials: I
authors.lastname: Ferrero
authors.forename: Claudia
authors.initials: C
authors.lastname: Donnini
mesh_terms: D000693:Anaerobiosis; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000935:Antifungal Agents / Q000494:pharmacology; D000968:Antimycin A / Q000494:pharmacology; D001692:Biological Transport; D050260:Carbohydrate Metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D005690:Galactose / Q000378:metabolism*; D005800:Genes, Fungal; D007716:Kluyveromyces / Q000187:drug effects / Q000378:metabolism; D008320:Maltose / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011887:Raffinose / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D027981:Symporters / Q000235:genetics / Q000502:physiology*
chemical_list: D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; D005656:Fungal Proteins; C106901:GAL2 protein, S cerevisiae; C095258:HXT7 protein, S cerevisiae; D009004:Monosaccharide Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D027981:Symporters; C049293:maltose permease, S cerevisiae; D000968:Antimycin A; D008320:Maltose; D011887:Raffinose; D005690:Galactose