SUMMARY: The inducible systems of uptake of β-D-galactopyranosides into and were studied under aerobic and anaerobic conditions, using both lactose and the non-metabolized analogue, methyl 1-thio-β-D-galactopyranoside (TMG). A common carrier served both substrates, and aerobic entry was by active transport, involving proton symport. The rate of uptake and the final equilibrium concentration were decreased on adding '-dicyclohexylcarbodiimide, diethylstilbestrol or antimycin A, and active transport was completely abolished by carbonyl cyanide -chlorophenylhydrazone. Uptake under anaerobic conditions differed markedly from that occurring aerobically: TMG was not concentrated anaerobically, even by strongly fermenting yeasts. Instead, it was transported into the cells by facilitated diffusion, which could sustain a rate of entry of over half the maximum rate observed aerobically. That this difference between aerobic and anaerobic transport into yeasts might apply to glycosides in general, was suggested by the finding that a strain of also took up maltose by active transport under aerobic conditions, but by facilitated diffusion anaerobically. By contrast, the amino acid, 2-aminoisobutyric acid, was concentrated by , even under anaerobic conditions. The significance of these findings in relation to the Kluyver effect is discussed.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error