InterPro: IPR001341 Aspartate kinase domain

Bacteria, plants and fungi metabolise aspartic acid to produce four amino acids - lysine, threonine, methionine and isoleucine - in a series of reactions known as the aspartate pathway. Additionally, several important metabolic intermediates are produced by these reactions, such as diaminopimelic acid, an essential component of bacterial cell wall biosynthesis, and dipicolinic acid, which is involved in sporulation in Gram-positive bacteria. Members of the animal kingdom do not posses this pathway and must therefore acquire these essential amino acids through their diet. Research into improving the metabolic flux through this pathway has the potential to increase the yield of the essential amino acids in important crops, thus improving their nutritional value. Additionally, since the enzymes are not present in animals, inhibitors of them are promising targets for the development of novel antibiotics and herbicides. For more information see [1].

Aspartate kinase (EC:2.7.2.4) (AK) catalyzes the first reaction in the aspartate pathway; the phosphorylation of aspartate. The product of this reaction can then be used in the biosynthesis of lysine or in the pathway leading to homoserine, which participates in the biosynthesis of threonine, isoleucine and methionine [2].

In bacteria there are three different aspartate kinase isozymes which differ in sensitivity to repression and inhibition by Lys, Met and Thr. AK1 and AK2 are bifunctional enzymes which both consist of an N-terminal AK domain and a C-terminal homoserine dehydrogenase domain. AK1 is involved in threonine biosynthesis and AK2, in that of methionine. The third isozyme, AK3 is monofunctional and involved in lysine synthesis. In archaea and plants there may be a single isozyme of AK which in plants is multifunctional.

This entry represents a region encoding aspartate kinase activity found in both the monofunctional and bifunctional enzymes.

Synonym(s): Aspartokinase