Proc. Natl. Acad. Sci. USA, published online 17 June 2013; doi:10.1073/pnas.1303568110

Dehydrophos is a broad-spectrum antibiotic produced by Streptomyces luridus that contains an aminophosphonate analog of dehydroalanine (δAla(P)). Cleavage of this phosphonotripeptide natural product by cellular peptidases releases methyl acetylphosphonate, which is a potent inhibitor of pyruvate dehydrogenase. Bougioukou et al. now report that the previously proposed mechanism for dehydrophos biosynthesis is incorrect. Analysis of the biosynthetic gene cluster suggested that it contains two putative 2-oxoglutarate/Fe(II)-dependent oxygenases, two putative alcohol dehydrogenases, two pyridoxal 5′-phosphate–dependent enzymes and two putative nonribosomal peptidyl transferases. The authors reconstituted and biochemically characterized several of these enzymes, and their experiments led them to propose a revised biosynthetic pathway with three phases. The first steps involve the formation of the C-P bond, a decarboxylation reaction and the reduction of phosphonoacetaldehyde to 2-hydroxyethylphosphonate, enzymatic reactions that have been observed in the biosynthetic pathways of other phosphonates. In the second part of the biosynthetic pathway, several enzymes convert 2-hydroxyethylphosphonate to L-Ala(P). The final phase involves two amide bond–forming reactions, monomethylation of the terminal phosphonic acid and the conversion of the C-C single bond adjacent to the phosphonate to a C-C double bond. Additional work is needed to uncover exactly how these enzymes efficiently catalyze such unusual biochemical transformations.