Bacterial biosynthesis of lysine is a potential target for novel antibacterial agents as it provides both lysine for protein synthesis and meso-diaminopimelate for construction of the bacterial peptidoglycan cell wall. Dihydropicolinate synthase (DHDPS) catalyses the first reaction of (S)-lysine biosynthesis: an aldol condensation between (S)-aspartate -semialdehyde and pyruvate. The product of the reaction is the unstable heterocycle (4S)-4-hydroxy-2,3,4,5-tetrahydro-(2S)-dipicolinate (HTPA), which is thought to undergo a non-enzymatic dehydration to (S)-2,3-dihydrodipicolinate, the substrate of the next enzyme in the (S)-lysine biosynthetic pathway, DHDPR (dihydrodipicolinate reductase). The sequences of DHDPS from different sources are well-conserved. Almost all DHDPS enzymes with known structures are homotetramers formed as a dimer of tight dimers. Each monomer comprises 2 domains: an 8-fold alpha-/beta-barrel, and a C-terminal alpha-helical domain. A catalytic triad (Tyr133, Thr44, Tyr107 in E. coli), enabling a proton shuttle from the active site to bulk solvent, and the active site lysine is located in the barrel domain.