ACT domains located C-terminal to the catalytic domain of the aspartokinase (AK) HOM3
This CD includes the second of two ACT domains located C-terminal to the catalytic domain of the aspartokinase (AK) HOM3, a monofunctional class enzyme found in Saccharomyces cerevisiae, and other related ACT domains. AK is the first enzyme in the aspartate metabolic pathway, catalyzes the conversion of aspartate and ATP to aspartylphosphate and ADP, and in fungi, is responsible for the production of threonine, isoleucine and methionine. S. cerevisiae has a single AK, which is regulated by feedback, allosteric inhibition by L-threonine. Recent studies shown that the allosteric transition triggered by binding of threonine to AK involves a large change in the conformation of the native hexameric enzyme that is converted to an inactive one of different shape and substantially smaller hydrodynamic size. Members of this CD belong to the superfamily of ACT regulatory domains.