AAK_AK-Ectoine: Amino Acid Kinase Superfamily (AAK), AK-Ectoine; this CD includes the N-terminal catalytic domain of the aspartokinase of the ectoine (1,4,5,6-tetrahydro-2-methyl pyrimidine-4-carboxylate) biosynthetic pathway found in Methylomicrobium alcaliphilum, Vibrio cholerae, and other various halotolerant or halophilic bacteria. Bacteria exposed to hyperosmotic stress accumulate organic solutes called 'compatible solutes' of which ectoine, a heterocyclic amino acid, is one. Apart from its osmotic function, ectoine also exhibits a protective effect on proteins, nucleic acids and membranes against a variety of stress factors. de novo synthesis of ectoine starts with the phosphorylation of L-aspartate and shares its first two enzymatic steps with the biosynthesis of amino acids of the aspartate family: aspartokinase and L-aspartate-semialdehyde dehydrogenase. The M. alcaliphilum and the V. cholerae aspartokinases are encoded on the ectABCask operon.
Jiyao W et al.(2023). "The conserved domain database in 2023.",