DELTA-AMINOLEVULINIC-ACID TRANSPORT IN SACCHAROMYCES-CEREVISIAE

1. This work represents the first approach to characterize the transpo rt system of haem pathway precursors, such as delta-aminolevulinic aci d (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 sourc e; this suggests a rather complex regulation mechanism. 3. This transp ort is not mediated by the general amino acid permease (GAP). 4. ALA u ptake is strongly inhibited by compounds harboring a methyl-amine term inus suggesting that this group is essential for ALA transport; howeve r, the electric environment of the carboxylic group may be also import ant for the interaction between ALA and its transporter active site. 5 . We have found differences in ALA transport which would indicate a di fferent regulation mechanism for this system in both strain cells.