Rapid kinetics of glucose uptake in Saccharomyces cerevisiae.
In a multiple deletion mutant hxt1deltahxt2deltahxt3delta hxt4deltasnf3delta of Saccharomyces cerevisiae growing on a 2% glucose, high-affinity glucose-uptake (low Km) 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. However, in a mutant containing only the HXT2 gene (hxt1deltahxt3deltahxt4deltasnf3delta), invertase levels were similar to those in the wild-type. It is likely, therefore, that some of these putative glucose transporters, such as HXT2, 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 (Km 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.
E.C. Slater Institute, University of Amsterdam, The Netherlands.
M C
MC
Walsh
H P
HP
Smits
M
M
Scholte
G
G
Smits
K
K
van Dam
D001692:Biological Transport; D005947:Glucose / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000378:metabolism; D007700:Kinetics; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion / Q000502:physiology; D043324:beta-Fructofuranosidase
D009004:Monosaccharide Transport Proteins; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase; D005947:Glucose