Lysine is biosynthesized from L-aspartic acid. L-Aspartic acid can be incorporated into the cell through various methods: C4 dicarboxylate/orotate:H+ symporter, glutamate/aspartate:H+ symporter GltP, dicarboxylate transporter, C4 dicarboxylate/C4 monocarboxylate transporter DauA, and glutamate/aspartate ABC transporter. L-Aspartic acid is phosphorylated by an ATP-driven aspartate kinase resulting in ADP and L-aspartyl-4-phosphate. L-Aspartyl-4-phosphate is then dehydrogenated through an NADPH-driven aspartate semialdehyde dehydrogenase resulting in a release of phosphate, NADP, and L-aspartic 4-semialdehyde (involved in methionine biosynthesis). L-Aspartic 4-semialdehyde interacts with a pyruvic acid through a 4-hydroxy-tetrahydrodipicolinate synthase resulting in a release of hydrogen ion, water, and (2S,4S)-4-hydroxy-2,3,4,5-tetrahydrodipicolinate. The latter compound is then reduced by an NADPH-driven 4-hydroxy-tetrahydrodipicolinate reductase resulting in a release of water, NADP, and (S)-2,3,4,5-tetrahydrodipicolinate, This compound interacts with succinyl-CoA and water through a tetrahydrodipicolinate succinylase resulting in a release of coenzyme A and N-succinyl-2-amino-6-ketopimelate. This compound interacts with L-glutamic acid through an N-succinyldiaminopimelate aminotransferase resulting in oxoglutaric acid and N-succinyl-L,L-2,6-diaminopimelate. The latter compound is then desuccinylated by reacting with water through an N-succinyl-L-diaminopimelate desuccinylase resulting in a succinic acid and L,L-diaminopimelate. This compound is then isomerized through a diaminopimelate epimerase resulting in a meso-diaminopimelate (involved in peptidoglycan biosynthesis I). This compound is then decarboxylated by a diaminopimelate decarboxylase resulting in a release of carbon dioxide and L-lysine. L-Lysine is then incorporated into the lysine degradation pathway. Lysine also regulates its own biosynthesis by repressing dihydrodipicolinate synthase and also by repressing lysine-sensitive aspartokinase 3. Diaminopielate is a precursor for lysine as well as other cell wall components. Synthesis of lysine starts by converting L-aspartic acid (L-aspartate) to L-Aspartyl-4-phosphate by aspartate kinase. L-Aspartyl-4-phosphate transforms to form L-aspartic 4-semialdehyde (L-aspartate semialdehyde) by aspartate semialdehyde dehydrogenase with NADPH. L-aspartic 4-semialdehyde can start the metabolic pathway of synthesis of methionine as well as synthesis of threonine. Aspartate kinase can be regulated by its end product: L-Lysine.

Lysine Biosynthesis References