Urea transport in Saccharomyces cerevisiae

Abstract

Urea transport in S. cerevisiae occurs by 2 pathways. The first mode of uptake is via an active transport system which has an apparent Km value of 14 μM, is absolutely dependent on energy metabolism, requires pregrowth of the cultures in the presence of oxaluric acid, gratuitous inducer of the allantoin degradative enzymes, and is sensitive to nitrogen repression. The second mode of uptake which occurs at external urea concentrations in excess of 0.5 mM is via either passive or facilitated diffusion.