Changes in the phosphatide pattern of yeast cells in relation to active carbohydrate transport

Galactose Transport in Saccharomyces cerevisiae III. Characteristics of Galactose Uptake in Transferaseless Cells: Evidence Against Transport-Associated Phosphorylation

“…The results from the studies on galactose uptake by galactokinaseless cells in the previous paper of this series suggest that both galactose and its nonmetabolized analogues are transported by a passive, carrier-mediated, facilitated diffusion and that the rate of galactose uptake by metabolizing cells is galactokinase-limited, not transportlimited. [The consequences of this fact on the sugar pool size in metabolizing cells has been treated elsewhere (9).] This conclusion is strongly supported by the results of the present paper on the rate of labeling of intracellular free galactose and galactose-l-phosphate.…”

“…Furthermore, by measuring the rate of galactose uptake under counterflow conditions, it was demonstrated that the rate of galactose uptake by facilitated diffusion in galactokinaseless cells is greater than the rate of galactose metabolism by wild-type cells over the same concentration range. Although the demonstration that the rate of galactose uptake by facilitated diffusion can 1 account for the rate of galactose metabolism eliminates the necessity for the special transportassociated phosphorylation mechanism proposed for galactose transport by Van Steveninck and his colleagues (9,23,28), this study investigates the possible importance of the phosphorylation pathway in transferaseless mutants. The rate of galactose uptake by transferaseless cells is almost identical with that of wild-type cells and results in the accumulation of a mixture of free galactose and galactose-l-phosphate.…”

“…In addition to the questionable validity of the interpretation of the effects of Ni2+ ions and IAA on galactose transport according to the Van Steveninck model, the model has other deficiencies. The "permease," although it is defined to be independent of the sugar kinases (hexokinase and galactokinase), acts as a phosphotransferase, carrying out the parallel function of sugar phosphorylation by using polyphosphate directly or indirectly (e.g., phosphatidyl glycerolphosphate derived from polyphosphate) as the phosphate donor (9,26,28). The model predicts that galactokinaseless cells should either be able to metabolize galactose by the transport-associated phosphorylation pathway or accumulate galactose by an active process.…”

Alterations in the Phospholipid Composition of Escherichia coli B During Growth at Different Temperatures

“…Booij have published some evidence that PG and PGP have a role in carbohydrate transport in yeast cells (8).…”

Transport Alterations in a Phosphatidylethanolamine-Deficient Mutant of Bacillus subtilis

“…A notable exception has been the accumulation of evidence which implicates phosphatidylglycerol with carbohydrate transport (4,12). Minimal evidence exists that links membrane lipids and amino acid transport insofar as certain radioisotopically labeled amino acids exhibit a tendency to bind to lipid (1,8,18).…”