Biomedical subjects

P S De Araujo

Publications and source records attributed to P S De Araujo.

4 recordsLinked to original sources

PubMed2000

Kinetics of active sucrose transport in Saccharomyces cerevisiae.

The kinetic analysis of active sucrose-H+ uptake by Saccharomyces cerevisiae revealed the presence of two transport systems with high and low affinity for sucrose. The MAL2T permease has a low affinity (K(m) = 120 +/-20 mM) for sucrose, while the alpha-glucoside transporter encoded by the AGT1 gene is a high affinity sucrose-H+ symporter (K(m) = 7.9+/-0.8 mM) that increases the specific growth rate of cells growing on sucrose.

Journal Article↗

PubMed1996

Kinetics and energetics of trehalose transport in Saccharomyces cerevisiae.

Cells of Saccharomyces cerevisiae are able to transport trehalose against a concentration gradient, without efflux or counterflow of the labeled substrate. Uptake was inhibited by uncouplers, acetic acid, and organic mercury compounds. The addition of trehalose resulted in alkalinization of the medium. The ratio of H+ depletion to trehalose uptake by yeast cells was approximately 1:1, which indicates the existence of a trehalose-H+ symporter in these cells. The optimum pH for this active H+-trehalose symport was 5.0, and both the Km and the Vmax were negatively affected by increasing or decreasing the extracellular pH from its optimum value. Kinetic studies showed the existence of at least two different trehalose transport activities in yeast cells: a high-affinity H+-trehalose symporter (Km = 4 mM), and a low-affinity transport activity (Km > 100 mM) that could be a facilitated diffusion process. The high-affinity H+-trehalose symporter was repressed by glucose, whereas the low-affinity uptake was constitutively expressed in S. cerevisiae.

Biological Transport, Active↗

PubMed1991

Trehalose transport in yeast cells.

Saccharomyces cerevisiae possesses a specific transporter for trehalose. Transport is low until after glucose exhaustion in stationary phase, and addition of glucose in stationary phase results in loss of transport, an event that is reversible when the glucose is removed. The effect of glucose is not competitive inhibition: the increase in trehalose transport in stationary phase requires a lag time after glucose is depleted; and recovery of transport after glucose inhibition requires protein synthesis. Finally, we provide evidence that the trehalose transporter is distinct from that for maltose.

Binding, Competitive↗

PubMed1991

Trehalose-transporting membrane vesicles from yeasts.

We have isolated and characterized a membrane vesicle fraction from yeasts that is capable trehalose transport. The kinetics of the transport system were similar to those seen in the intact cells. The transport depends on a transmembrane pH gradient. If the gradient is collapsed, trehalose accumulated inside the vesicles is leaked into the medium. After aging for several days the ability of the vesicles to transport was lost. However, transport was partially restored by elevating internal pH in the vesicles.

Biological Transport↗