ACT domains of the diaminopimelate-sensitive aspartokinase (AK) isoenzyme AKI
This CD includes the C-terminal of the two ACT domains of the diaminopimelate-sensitive aspartokinase (AK) isoenzyme AKI, a monofunctional class enzyme found in Bacilli (Bacillus subtilis (BS) strain 168), Clostridia, and Actinobacteria bacterial species. In B. subtilis, the regulation of the diaminopimelate-lysine biosynthetic pathway involves dual control by diaminopimelate and lysine, effected through separate diaminopimelate- and lysine-sensitive AK isoenzymes. AKI activity is invariant during the exponential and stationary phases of growth and is not altered by addition of amino acids to the growth medium. The role of this isoenzyme is most likely to provide a constant level of aspartyl-beta-phosphate for the biosynthesis of diaminopimelate for peptidoglycan synthesis and dipicolinate during sporulation. The BS AKI is tetrameric consisting of two alpha and two beta subunits; the alpha (43 kD) and beta (17 kD) subunit formed by two in-phase overlapping genes. The alpha subunit contains the AK catalytic domain and two ACT domains. The beta subunit contains two ACT domains. Members of this CD belong to the superfamily of ACT regulatory domains.