Rapid kinetics of glucose uptake inSaccharomyces cerevisiae |
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Authors: | M. C. Walsh H. P. Smits M. Scholte G. Smits K. van Dam |
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Affiliation: | (1) E.C. Slater Institute, BioCentrum Amsterdam, University of Amsterdam, 1018 TV Amsterdam, The Netherlands |
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Abstract: | In a multiple deletion mutanthxt1Δhxt2Δhxt3Δ hxt4Δsnf3Δ ofSaccharomyces cerevisiae growing on 2 % glucose, high-affinity glucose-uptake (lowK m) was exhibited throughout growth on glucose in contrast to the wild-type, which exhibited the usual low-affinity to high-affinity transition as the glucose in the medium was consumed. elevated levels of invertase activity throughout growth on glucose, in this mutant as compared to the wild-type, indicate that glucose repression may be impaired. Howver, in a mutant containing only theHXT2 gene (hxt1Δhxt3Δhxt4Δ snf3Δ), invertase levels were similar to those in the wild-type. It is likely, therefore, that some of these putative glucose transporters, such asHXT2, also have regulatory roles in cellular metabolism. In triple hexose-kinase mutants, rapid (200-ms) measurements of initial glucose-uptake revealed high-affinity glucose uptake (K m approx. 2 mmol/L) while measurements on the slower 5-s scale clearly demonstrate that uptake is not linear over this longer period. These results suggest that this high-affinity component does not require a functional hexose-kinase. |
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