Cloning and characterization of the first two genes of the non-oxidative part of the Saccharomyces cerevisiae pentose-phosphate pathway.
We have cloned and characterized the two remaining unknown genes of the non-oxidative part of the pentose-phosphate pathway of Saccharomyces cerevisiae encoding the enzymes D-ribulose-5-phosphate 3-epimerase (Rpe1p) and D-ribose-5-phosphate ketol-isomerase (Rki1p). Rpe1p has an unexpected high specific activity of 2148 mU x (mg protein)-1 in crude extracts. Deletion mutants of RPE1 show no enzyme activity and are unable to grow on D-xylulose. Unexpectedly, haploid rki1 deletion mutants are not viable. Functional expression of RKI1 was demonstrated following an increase of gene dosage in the haploid rki1 deletion mutant, which restored viability and specific D-ribose-5-phosphate ketol-isomerase activity. Both enzymes show high similarity to the deduced protein sequences of various open reading frames, expressed sequence tags or cDNAs from different organisms.
Miosga
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Institut für Mikrobiologie und Genetik, Technische Hochschule Darmstadt, Schnittspahnstrasse 10, D-64287 Darmstadt, Germany.
Zimmermann
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FK
D019747:Aldose-Ketose Isomerases; D002238:Carbohydrate Epimerases / Q000235:genetics*; D003001:Cloning, Molecular; D018076:DNA, Complementary; D001330:Electronic Data Processing; D017353:Gene Deletion; D018628:Gene Dosage; D015966:Gene Expression Regulation, Fungal; D006238:Haploidy; D016366:Open Reading Frames; D010957:Plasmids; D019998:Racemases and Epimerases / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology*; D012689:Sequence Homology, Nucleic Acid; D014996:Xylulose / Q000378:metabolism
D018076:DNA, Complementary; D014996:Xylulose; D019998:Racemases and Epimerases; D002238:Carbohydrate Epimerases; D019747:Aldose-Ketose Isomerases; C022548:ribosephosphate isomerase