Studies on the Biosynthesis of Tabtoxin (Wildfire Toxin). Origin of the Carbonyl C-Atom of the β-Lactam Moiety from the C1-Pool

Article abstract of DOI:10.1002/hlca.19870700220

Re-isolation of Pseudomonas tabaci strain NCPPB 2730 from its host, the tobacco plant, led to an activation of the bacteria in order to produce the β-lactam dipeptide tabtoxin (Wildfire toxin, 1).Incorporation of several 14C-labelled amino acids, as well as L-methionine, L-<1,2-(13)C2>- and L-<3,4-(13)C2>aspartate, rac-<1,2-(13)C2>glycerol, and <1,2-(13)C2>acetate into isotabtoxin (2) demonstrated that the building blocks of tabtoxin (1) are L-threonine, L-aspartate, the Me group of L-methionine and a C₂-unit derived from the C₃-pool.The Me gruop of L-methionine provides the carbonyl C-atom of the β-lactam moiety.These findings represent a novel pathway in β-lactam biosynthesis.Mechanistic aspects with respect to the β-lactam ring formation are discussed.A biradical 16 is proposed as an intermediate during the cyclization of a N-formyl-α-amino ketone 15.