The pentose phosphate pathway (PPP) is essential for human health and provides, amongst others, the reduction power to cope with oxidative stress. In contrast to the model baker’s yeast, the PPP also contributes to a large extent to glucose metabolism in the milk
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The pentose phosphate pathway (PPP) is essential for human health and provides, amongst others, the reduction power to cope with oxidative stress. In contrast to the model baker’s yeast, the PPP also contributes to a large extent to glucose metabolism in the milk yeast
Kluyveromyces lactis. Yet, the physiological consequences of mutations in genes encoding PPP enzymes in
K. lactis have been addressed for only a few. We here embarked on a systematic study of such mutants, deleting
ZWF1,
SOL4,
GND1,
RKI1,
RPE1,
TKL1,
TAL1, and
SHB17. Interestingly,
GND1,
RKI1, and
TKL1 were found to be essential under standard growth conditions. Epistasis analyses revealed that a lack of Zwf1 rescued the lethality of the
gnd1 deletion, indicating that it is caused by the accumulation of 6-phosphogluconate. Moreover, the slow growth of a
tal1 null mutant, which lacks fructose-1,6-bisphosphate aldolase, was aggravated by deleting the
SHB17 gene encoding sedoheptulose-1,7-bisphosphatase. A mitotically stable
tetOFF system was established for conditional expression of
TAL1 and
TKL1, encoding transaldolase and transketolase in the non-oxidative part of the PPP, and employed in a global proteome analysis upon depletion of the enzymes. Results indicate that fatty acid degradation is upregulated, providing an alternative energy source. In addition,
tal1 and
tkl1 null mutants were complemented by heterologous expression of the respective genes from baker’s yeast and humans. These data demonstrate the importance of the PPP for basic sugar metabolism and oxidative stress response in
K. lactis and the potential of this yeast as a model for the study of PPP enzymes from heterologous sources, including human patients.
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