DELTA-AMINOLEVULINIC-ACID TRANSPORT IN SACCHAROMYCES-CEREVISIAE

1. This work represents the first approach to characterize the transport system of haem pathway precursors, such as delta-aminolevulinic acid (ALA), in two strains of Saccharomyces cerevisiae, a wild type, D27, and a HEM R(+) mutant. 2. ALA transport occurs unidirectionally by a sole active system with an apparent K-M of 0.10 mM, at the optimum pH of 5.0. ALA uptake is influenced by both the carbon and nitrogen source; this suggests a rather complex regulation mechanism. 3. This transport is not mediated by the general amino acid permease (GAP). 4. ALA uptake is strongly inhibited by compounds harboring a methyl-amine terminus suggesting that this group is essential for ALA transport; however, the electric environment of the carboxylic group may be also important for the interaction between ALA and its transporter active site. 5. We have found differences in ALA transport which would indicate a different regulation mechanism for this system in both strain cells.