>gnl|CDD|58600 cd04234, AAK_AK, AAK_AK: Amino Acid Kinase Superfamily (AAK), Aspartokinase (AK); this CD includes the N-terminal catalytic domain of aspartokinase (4-L-aspartate-4-phosphotransferase;). AK is the first enzyme in the biosynthetic pathway of the aspartate family of amino acids (lysine, threonine, methionine, and isoleucine) and the bacterial cell wall component, meso-diaminopimelate. It also catalyzes the conversion of aspartate and ATP to aspartylphosphate and ADP. One mechanism for the regulation of this pathway is by the production of several isoenzymes of aspartokinase with different repressors and allosteric inhibitors. Pairs of ACT domains are proposed to specifically bind amino acids leading to allosteric regulation of the enzyme. In Escherichia coli, three different aspartokinase isoenzymes are regulated specifically by lysine, methionine, and threonine. AK-HSDHI (ThrA) and AK-HSDHII (MetL) are bifunctional enzymes that consist of an N-terminal AK and a C-terminal homoserine dehydrogenase (HSDH). ThrA and MetL are involved in threonine and methionine biosynthesis, respectively. The third isoenzyme, AKIII (LysC), is monofunctional and is involved in lysine synthesis. The three Bacillus subtilis isoenzymes, AKI (DapG), AKII (LysC), and AKIII (YclM), are feedback-inhibited by meso-diaminopimelate, lysine, and lysine plus threonine, respectively. The E. coli lysine-sensitive AK is described as a homodimer, whereas, the B. subtilis lysine-sensitive AK is described as a heterodimeric complex of alpha- and beta- subunits that are formed from two in-frame overlapping genes. A single AK enzyme type has been described in Pseudomonas, Amycolatopsis, and Corynebacterium. The fungal aspartate pathway is regulated at the AK step, with L-Thr being an allosteric inhibitor of the Saccharomyces cerevisiae AK (Hom3). At least two distinct AK isoenzymes can occur in higher plants, one is a monofunctional lysine-sensitive isoenzyme, which is involved in the overall regulation of the pathway and can be synergistically inhibited by S-adenosylmethionine. The other isoenzyme is a bifunctional, threonine-sensitive AK-HSDH protein. Also included in this CD is the catalytic domain of the Methylomicrobium alcaliphilum ectoine AK, the first enzyme of the ectoine biosynthetic pathway, found in this bacterium, and several other halophilic/halotolerant bacteria.. Length = 227

 Score = 58.6 bits (142), Expect = 2e-09
 Identities = 36/109 (33%), Positives = 57/109 (52%), Gaps = 12/109 (11%)

Query: 127 SQGKVVI---FSGGTGNAFLTT------DSAAALRASEIGADVILKGTQVDGVYSADPRV 177
             GKV +   F G   +  +TT      D +AA  A+ +GAD +   T VDG+Y+ADPR+
Sbjct: 111 EIGKVPVVTGFIGRNEDGEITTLGRGGSDYSAAALAAALGADEVEIWTDVDGIYTADPRI 170

Query: 178 HASSTRFDSLTYNQFIE---KGLKVMDCASVVLARDCSIPIIVFSIHSP 223
              +     ++Y++ +E    G KV+   +V  AR  +IPI V +  +P
Sbjct: 171 VPEARLIPEISYDEALELAYFGAKVLHPRAVEPARKANIPIRVKNTFNP 219