The enzyme 5-aminolaevulinic acid dehydratase (ALAD) is responsible for the synthesis of porphobilinogen (PBG) from two molecules of 5-aminolaevulinic acid (ALA). Porphobilinogen is an important committed intermediate in the biosynthesis of tetrapyrroles. The inhibition of ALAD from the purple bacterium Rhodopseudomonas sphaeroides was tested with various substrate and product analogues. Excellent inhibition was observed ...