Dihydrodipicolinate Synthase

In enzymology, a dihydrodipicolinate synthase (EC 4.2.1.52) is an enzyme that catalyzes the chemical reaction

L-aspartate 4-semialdehyde + pyruvate (S)-2,3-dihydropyridine-2,6-dicarboxylate + 2 H2O

Thus, the two substrates of this enzyme are L-aspartate 4-semialdehyde and pyruvate, whereas its two products are (S)-2,3-dihydropyridine-2,6-dicarboxylate and H2O.

This enzyme belongs to the family of lyases, specifically the hydro-lyases, which cleave carbon-oxygen bonds. The systematic name of this enzyme class is L-aspartate-4-semialdehyde hydro-lyase . Other names in common use include dihydropicolinate synthetase (DHDPS), dihydrodipicolinic acid synthase, L-aspartate-4-semialdehyde hydro-lyase (adding pyruvate and, and cyclizing). This enzyme participates in lysine biosynthesis.

Dihydropicolinate synthase is the key enzyme in lysine biosynthesis via the diaminopimelate pathway of prokaryotes, some phycomycetes and higher plants. The enzyme catalyses the condensation of L-aspartate-beta- semialdehyde and pyruvate to dihydropicolinic acid via a ping-pong mechanism in which pyruvate binds to the enzyme by forming a Schiff base with a lysine residue. Three other proteins are structurally related to DHDPS and probably also act via a similar catalytic mechanism. These are Escherichia coli N-acetylneuraminate lyase (EC 4.1.3.3) (gene nanA), which catalyses the condensation of N-acetyl-D-mannosamine and pyruvate to form N-acetylneuraminate; Rhizobium meliloti (Sinorhizobium meliloti) protein mosA, which is involved in the biosynthesis of the rhizopine 3-o-methyl-scyllo-inosamine; and E. coli hypothetical protein yjhH. The sequences of DHDPS from different sources are well-conserved. The structure takes the form of a homotetramer, in which 2 monomers are related by an approximate 2-fold symmetry. Each monomer comprises 2 domains: an 8-fold alpha-/beta-barrel, and a C-terminal alpha-helical domain. The fold resembles that of N-acetylneuraminate lyase. The active site lysine is located in the barrel domain, and has access via 2 channels on the C-terminal side of the barrel.

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