The enzyme catalyses the asymmetric condensation and cyclization of two 5-aminolevulinate molecules, which is the first common step in the biosynthesis of tetrapyrrole pigments such as porphyrin, chlorophyll, vitamin B12, siroheme, phycobilin, and cofactor F430. The enzyme is widespread, being essential in organisms that carry out respiration, photosynthesis, or methanogenesis. The enzymes from most organisms utilize metal ions (Zn2+, Mg2+, K+, and Na+) as cofactors that reside at multiple sites, including the active site and allosteric sites. Enzymes from archaea, yeast, and metazoa (including human) contain Zn2+ at the active site. In humans, the enzyme is a primary target for the environmental toxin Pb. The enzymes from some organisms utilize a dynamic equilibrium between architecturally distinct multimeric assemblies as a means for allosteric regulation.
The taxonomic range for the selected organisms is: Pseudomonas aeruginosa The expected taxonomic range for this enzyme is: Bacteria, Eukaryota, Archaea
catalytic mechanism initiated by a C-C bond formation between A and P-side 5-aminolevulinic acid, followed by the formation of the intersubstrate Schiff base yielding the product porphobilinogen
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SYSTEMATIC NAME
IUBMB Comments
5-aminolevulinate hydro-lyase (adding 5-aminolevulinate and cyclizing; porphobilinogen-forming)
The enzyme catalyses the asymmetric condensation and cyclization of two 5-aminolevulinate molecules, which is the first common step in the biosynthesis of tetrapyrrole pigments such as porphyrin, chlorophyll, vitamin B12, siroheme, phycobilin, and cofactor F430. The enzyme is widespread, being essential in organisms that carry out respiration, photosynthesis, or methanogenesis. The enzymes from most organisms utilize metal ions (Zn2+, Mg2+, K+, and Na+) as cofactors that reside at multiple sites, including the active site and allosteric sites. Enzymes from archaea, yeast, and metazoa (including human) contain Zn2+ at the active site. In humans, the enzyme is a primary target for the environmental toxin Pb. The enzymes from some organisms utilize a dynamic equilibrium between architecturally distinct multimeric assemblies as a means for allosteric regulation.
enzymatic mechanism starts with formation of a C-C bond, linking C3 of the A-side 5-aminolevulinic acid to C4 of the P-side 5-aminolevulinic acid through an aldole addition
binds only 4 Mg2+ per octamer, these 4 Mg2+ allosterically stimulate a metal ion independent catalytic actiovity, in a fashion dependent upon both pH and K+, the allosteric Mg2+ is located in metal binding site C, which is outside the active site. NO evidence is found for metal binding to the potential high-affinity active site metal binding site A and/or B, no direct involvement of Mg2+ in substrate binding and product formation
porphobilinogen synthase is cocrystallized with the alaremycin. At 1.75 A resolution, the crystal structure reveals that the antibiotic efficiently blocks the active site of porphobilinogen synthase. The antibiotic binds as a reduced derivative of 5-acetamido-4-oxo-5-hexenoic acid. The corresponding methyl group is not coordinated by any amino acid residues of the active site, excluding its functional relevance for alaremycin inhibition. Alaremycin is covalently bound by the catalytically important active-site lysine residue 260 and is tightly coordinated by several active-site amino acids
hanging drop vapor-diffusion method. Crystal structures of the active site of Pseudomonas aeruginosa PBGS with the various inhibitors 5-hydroxylevulinic acid, 5,5'-oxybis(4-oxopentanoic acid), 5,5'-iminobis(4-oxopentanoic acid), 5,5'-thiobis(4-oxopentanoic acid), 5,5'-sulfinylbis(4-oxopentanoic acid) or 5,5'-sulfonylbis(4-oxopentanoic acid)
hanging drop vapour diffusion method, crystals of the enzyme complex with levulinic acid solved at 1.67 A resolution, crystals belong to space group P42(1)2 with cell dimensions of a = b = 129.8 A, c = 86.7 A
Frankenberg, N.; Kittel, T.; Hungerer, C.; Rrnemann, D.
Cloning, mapping and functional characterization of the hemB gene of Pseudomonas aeruginosa, which encodes a magnesium-dependent 5-aminolevulinic acid dehydratase