Lysine

Route: Aspartate semialdehyde + Pyruvate → 4-Hydroxy-2,3,4,5-tetrahydrodipicolinate → 2,3,4,5-Tetrahydrodipicolinate → N-Succinyl-2-amino-6-ketopimelate → N-Succinyl-L,L-diaminopimelate → L,L-Diaminopimelate → meso-Diaminopimelate → Lysine

Humans cannot make lysine, so it is an essential amino acid that must come from food. Bacteria and plants make it through diaminopimelate (DAP), shown here in the succinylase variant used by E. coli. Other bacteria use an acetyl group in place of the succinyl group, and a limited number of species use a single dehydrogenase step. Fungi use a different route, the alpha-aminoadipate pathway. Aspartate semialdehyde condenses with pyruvate, and the ring that forms is reduced with NADPH. The ring is opened by water after succinyl-CoA adds a succinyl group to the ring nitrogen. A transamination from glutamate adds the second amino group, and the succinyl group is then removed. An epimerase flips one of the two stereo centers, which turns L,L-diaminopimelate into the meso form, which has one R and one S center. The last enzyme, which needs pyridoxal phosphate, removes one carboxyl group and leaves L-lysine. Meso-diaminopimelate is also a building block of the cell wall in many bacteria.

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Steps

Enzyme names and EC numbers are those used on the interactive board. Checked against sources: see the claim table in the repository (tools/pathway_data/checks).