Transport and metabolic effects of alpha-aminoisobutyric acid in Saccharomyces cerevisiae.
alpha-Aminoisobutyric acid is actively transported into yeast cells by the general amino acid transport system. The system exhibits a Km for alpha-aminoisobutyric acid of 270 microM, a Vmax of 24 nmol/min per mg cells (dry weight), and a pH optimum of 4.1-4.3. alpha-Aminoisobutyric acid is also transported by a minor system(s) with a Vmax of 1.7 nmol/min per mg cells. Transport occurs against a concentration gradient with the concentration ratio reaching over 1000:1 (in/out). The alpha-aminoisobutyric acid is not significantly metabolized or incorporated into protein after an 18 h incubation. alpha-Aminoisobutyric acid inhibits cell growth when a poor nitrogen source such as proline is provided but not with good nitrogen sources such as NH+4. During nitrogen starvation alpha-aminoisobutyric acid strongly inhibits the synthesis of the nitrogen catabolite repression sensitive enzyme, asparaginase II. Studies with a mutant yeast strain (GDH-CR) suggest that alpha-aminoisobutyric acid inhibition of asparaginase II synthesis occurs because alpha-aminoisobutyric acid is an effective inhibitor of protein synthesis in nitrogen starved cells.
D000596:Amino Acids / Q000378:metabolism / Q000494:pharmacology; D000621:Aminoisobutyric Acids / Q000378:metabolism* / Q000494:pharmacology; D001692:Biological Transport; D007700:Kinetics; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
D000596:Amino Acids; D000621:Aminoisobutyric Acids; C100049:2-aminoisobutyric acid