Oxalurate transport in Saccharomyces cerevisiae

Oxalurate, the gratuitous inducer of the allantoin degradative enzymes, was taken into the cell by an energy-dependent active transport system with an apparent Km of 1.2 mM. Efflux of previously accumulated oxalurate was rapid, with a half-life of about 2 min. The oxalurate uptake system appears to be both constitutively produced and insensitive to nitrogen catabolite repression. The latter observations suggest that failure of oxalurate to bring about induction of allophanate hydrolase in cultures growing under repressive conditions does not result from inducer exclusion, but rather from repression of dur1,2 gene expression.