Molecular analysis of the structural gene for yeast transaldolase

Authors

  • Ine SCHAAFF,

    Corresponding author
    1. Institut für Mikrobiologie, Technische Hochschule Darmstadt, Federal Republic of Germany
      Correspondence to I. Schaaff, Institut für Mikrobiologie, Technische Hochschule Darmstadt, Schnittspahnstrasse 10, D-6100 Darmstadt, Federal Republic of Germany
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  • Stefan HOHMANN,

    1. Institut für Mikrobiologie, Technische Hochschule Darmstadt, Federal Republic of Germany
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  • Friedrich K. ZIMMERMANN

    1. Institut für Mikrobiologie, Technische Hochschule Darmstadt, Federal Republic of Germany
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  • Note. The sequence data described in Fig. 6 appear in the EMBL/GenBank/DDBJ Nucleotide Sequence Databases under the acession number X15953 S. cerevisiae TAL1.

Correspondence to I. Schaaff, Institut für Mikrobiologie, Technische Hochschule Darmstadt, Schnittspahnstrasse 10, D-6100 Darmstadt, Federal Republic of Germany

Abstract

We have cloned the structural gene for yeast transaldolase. Transformants carrying the TAL1 gene on a multicopy plasmid over-produced transaldolase. A deletion mutant which was constructed using the cloned gene did not show any detectable transaldolase activity in vitro. Furthermore, both transaldolase isoenzymes which were detected in wild-type crude extracts by immunoblotting were missing in the deletion mutants. Thus, TAL1 is the only transaldolase structural gene in yeast.

TAL1 is not an essential gene. Deletion of the transaldolase gene did not affect growth on complete media with different carbon sources or on synthetic media. However, the transaldolase-deficient strains accumulated sedoheptulose 7-phosphate, an intermediate of the pentose-phosphate pathway. Mutants lacking both transaldolase and phosphoglucose isomerase grew more slowly than the single mutants. They accumulated more sedoheptulose 7-phosphate on medium containing fructose than on glucose medium. This shows that fructose 6-phosphate and glyceraldehyde 3-phosphate, metabolites of glycolysis, can enter the nonoxidative part of the pentose-phosphate pathway.

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