Genetic evidence that high noninduced maltase and maltose permease activities, governed by MALx3 encoded transcriptional regulators, determine efficiency of gas production by baker's yeast in unsugared dough (original) (raw)
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Α-Glucosidase, Α-Glucoside Permease, Maltose Fermentation and Leavening Ability of Baker's Yeast
Journal of the Institute of Brewing, 1975
a-Glucosidase and a-glucoside permease are synthesized simultaneously in two different strains of baker's yeast (Saccharomyces cerevisiae) when the cells are induced with maltose. oc-Thioethyl D-glucopyranoside (a-TEG) inhibits the transport of maltose into the cells, and the transport of maltose and a-TEG appeared to be mediated by the same permease system. There is an obvious correlation between a-glucosidase, a-glucoside permease and maltose fermentation activities in the yeasts while no correlation between these and the leavening ability of the yeasts can be demonstrated. Apparently the glucose concentration in dough is high enough to inhibit the permease-mediated transport of maltose into the cells thus impairing leavening ability from the maltose fermenting system.
Molecular and Cellular Biology
Maltose fermentation in Saccharomyces carlsbergensis is dependent upon the MAL6 locus. This complex locus is composed of the MAL61 and MAL62 genes, which encode maltose permease and maltase, respectively, and a third gene, MAL63, which codes for a trans-acting positive regulatory product. In wild-type strains, expression of the MAL61 and MAL62 mRNAs and proteins is induced by maltose and induction is dependent upon the MAL63 gene. Mutants constitutively expressing the MAL61 and MAL62 gene products have been isolated in ma163 backgrounds, and the mutations which have been analyzed map to a fourth MAL6-linked gene, MAL64. Cloning and characterization of this new gene are described in this report. The results revealed that the MAL64-C alleles present in constitutive strains encode a trans-acting positive function required for constitutive expression of the MAL61 and MAL62 gene products. In inducible strains, the MAL64 gene is dispensible, as deletion of the gene had no effect on maltose fermentation or maltose-regulated induction. MAL64 encoded transcripts of 2.0 and 1.4 kilobase pairs. While both MAL64 mRNAs were constitutively expressed in constitutive strains, they were maltose inducible in wild-type strains and induction was dependent upon the MAL63 gene. The MAL63 and MAL64 genes are at least partially structurally homologous, suggesting that they control MAL61 and MAL62 transcript accumulation by similar mechanisms.
MAL63 codes for a positive regulator of maltose fermentation in Saccharomyces cerevisiae
Current Genetics, 1988
Genetic analysis of the MAL6 locus has previously yielded mal6 mutants which fall into a single complementation group and which are noninducibte for maltase and maltose permease. However, the strains used in these studies contained additional partially functional copies of MALl (referred to as MALlg) and MAL3 (referred to as MAL3g). Using a strain lacking MALg genes, we have isolated two classes of mutants and these classes correspond to mutations in MAL63 and MAL61, two genes of the MAL6 complex. Disruptions of MAL63 are noninducible for maltase and maltose permease and for their corresponding mRNAs. The real6 mutants are shown to map to MAL63. Inducer exclusion as a cause of the noninducible phenotype of the real63 mutations has been eliminated by constructing a ma163 mutant in a strain constitutive for maltose permease; the strain remains noninducible. These results rigorously demonstrate that MAL63 is a regulatory gene which plays a positive role in the regulation of maltose fermentation.
2009
We performed an analysis of maltotriose utilization by 52 Saccharomyces yeast strains able to ferment maltose efficiently and correlated the observed phenotypes with differences in the copy number of genes possibly involved in maltotriose utilization by yeast cells. Methods and Results: The analysis of maltose and maltotriose utilization by laboratory and industrial strains of the species Saccharomyces cerevisiae and Saccharomyces pastorianus (a natural S. cerevisiae ⁄ Saccharomyces bayanus hybrid) was carried out using microscale liquid cultivation, as well as in aerobic batch cultures. All strains utilize maltose efficiently as a carbon source, but three different phenotypes were observed for maltotriose utilization: efficient growth, slow ⁄ delayed growth and no growth. Through microarray karyotyping and pulsed-field gel electrophoresis blots, we analysed the copy number and localization of several maltose-related genes in selected S. cerevisiae strains. While most strains lacked the MPH2 and MPH3 transporter genes, almost all strains analysed had the AGT1 gene and increased copy number of MALx1 permeases. Conclusions: Our results showed that S. pastorianus yeast strains utilized maltotriose more efficiently than S. cerevisiae strains and highlighted the importance of the AGT1 gene for efficient maltotriose utilization by S. cerevisiae yeasts. Significance and Impact of the Study: Our results revealed new maltotriose utilization phenotypes, contributing to a better understanding of the metabolism of this carbon source for improved fermentation by Saccharomyces yeasts.
FEMS Yeast Research, 2005
Hansenula polymorpha uses maltase to grow on maltose and sucrose. Inspection of genomic clones of H. polymorpha showed that the maltase gene HPMAL1 is clustered with genes corresponding to Saccharomyces cerevisiae maltose permeases and MAL activator genes orthologues. We sequenced the H. polymorpha maltose permease gene HPMAL2 of the cluster. The protein (582 amino acids) deduced from the HPMAL2 gene is predicted to have eleven transmembrane domains and shows 39-57% identity with yeast maltose permeases. The identity of the protein is highest with maltose permeases of Debaryomyces hansenii and Candida albicans. Expression of the HPMAL2 in a S. cerevisiae maltose permease-negative mutant CMY1050 proved functionality of the permease protein encoded by the gene. HPMAL1 and HPMAL2 genes are divergently positioned similarly to maltase and maltose permease genes in many yeasts. A two-reporter assay of the expression from the HPMAL1-HPMAL2 intergenic region showed that expression of both genes is coordinately regulated, repressed by glucose, induced by maltose, and that basal expression is higher in the direction of the permease gene.
Maltose fermentation and leavening ability of baker's yeast
European Journal of Applied Microbiology, 1977
Baker's yeasts with completely different a-glucoside permease, aglucosidase and maltose fermentation activities may still be almost equivalent in their leavening ability. A repression of the maltose uptake system of yeast occurs in a medium that besides maltose contains glucose or fructose. Hardly any maltose is utilized until the concentration of monosaccharide falls below 0.2% and a derepression of the maltose uptake system starts. It is almost conceivable that the repression also takes place in dough, as the hexose content of wheat flour is high enough to repress the maltose uptake system. The activities of the maltose fermenting system do not influence the leavening ability of the yeast as measured for the first hour of proofing, although maltose is the predominant sugar present.
Journal of Bacteriology
Saccharomyces yeasts ferment several aL-glucosides including maltose, maltotriose, turanose, a-methylglucoside, and melezitose. In the utilization of these sugars transport is the rate-limiting step. Several groups of investigators have described the characteristics of the maltose permease (D. E. Kroon and V. V. Koningsberger, Biochim. Biophys. Acta 204:590-609, 1970; R. Serrano, Eur. J. Biochem. 80:97-102, 1977). However, Saccharomyces contains multiple aL-glucoside transport systems, and these studies have never been performed on a genetically defined strain shown to have only a single permease gene. In this study we isolated maltose-negative mutants in a MAL6 strain and, using a high-resolution mapping technique, we showed that one class of these mutants, the group A mutants, mapped to the MAL61 gene (a member of the MAL6 gene complex). An insertion into the N-terminal-coding region of MAL61 resulted in the constitutive production of MAL61 mRNA and rendered the maltose permease similarly constitutive. Transformation by high-copynumber plasmids containing the MAL61 gene also led to an increase in the maltose permease. A deletiondisruption of MAL61 completely abolished maltose transport activity. Taken together, these results prove that this strain has only a single maltose permease and that this permease is the product of the MAL61 gene. This permease is able to transport maltose and turanose but cannot transport maltotriose, at-methylglucoside, or melezitose. The construction of strains with only a single permease will allow us to identify other maltoseinducible transport systems by simple genetic tests and should lead to the identification and characterization of the multiple genes and gene products involved in a-glucoside transport in Saccharomyces yeasts.
Journal of Bacteriology
Saccharomyces yeast strains able to ferment maltose carty at least one member of a family of MAL loci: MAL], MAL2, MAL3, MAL4, and MAL6. The MAL6 locus has been cloned and shown to be a cluster of at least three transcribed regions, all of which are required for maltose fermentation. Transcription at two of these genes, MAL61 and MAL62, is both induced by maltose and repressed by glucose. The third gene, MAL63, appears to encode a regulatory product controlling mnaltose fermentation. In this report, we demonstrate that the MAL62 gene is the structural gene coding for the enzyme maltase. Strain 332-5A is a maltose fermenter of the genotype MAL6 mad)0. Integrative disruption of the MAL62 gene of the MAL6 locus produces a strain which is still capable of fermenting maltose, but which synthesizes a more heat-labile form of maltase than the undisrupted strain. Synthesis of this more heat-labile maltase was shown to be linked to the mall°locus present in the strain. Integrative disruption of both the MAL62 gene and the MAL62-homologous sequence present at the mall°locus produces a nonfermenter which is unable to synthesize maltase. These results identify MAL62 as the maltase structural gene.
FEBS Letters, 1997
In Saccharomyces cerevisiae maltose utilization requires a functional MAL locus, each composed of three genes: MALR (gene 3) encoding a regulatory protein, MALT (gene 1) encoding maltose permease and MALS (gene 2) encoding maltase. We show that constitutive activation of the RAS/protein kinase A pathway severely reduces growth of MAL1 strains on maltose. This may be a consequence of reduction in MALT mRNA, reduced V max and increased catabolite inactivation of the MALT‐encoded maltose transporter in the MAL1 strain. Mutations in the GGS1/TPS1 gene, which restricts glucose influx and possibly affects signalling, relieve carbon catabolite repression on both maltase and maltose permease and reduce maltose permease inactivation.
Genetics, 2000
Expression of the MAL genes required for maltose fermentation in Saccharomyces cerevisiae is induced by maltose and repressed by glucose. Maltose-inducible regulation requires maltose permease and the MAL-activator protein, a DNA-binding transcription factor encoded by MAL63 and its homologues at the other MAL loci. Previously, we showed that the Mig1 repressor mediates glucose repression of MAL gene expression. Glucose also blocks MAL-activator-mediated maltose induction through a Mig1p-independent mechanism that we refer to as glucose inhibition. Here we report the characterization of this process. Our results indicate that glucose inhibition is also Mig2p independent. Moreover, we show that neither overexpression of the MAL-activator nor elimination of inducer exclusion is sufficient to relieve glucose inhibition, suggesting that glucose acts to inhibit induction by affecting maltose sensing and/or signaling. The glucose inhibition pathway requires HXK2, REG1, and GSF1 and appear...