Information on EC 4.2.1.24 - porphobilinogen synthase

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.