Wildfire toxin

These "suicide reagents" will be described in detail elsewhere in this volume (44), so only one phase will be briefly mentioned here. Of particular interest to food and nutrition researchers are the naturally occurring toxins which involve a "suicide" mechanism (42). Some of these can be consumed in foods or feeds and commonly occur in a number of different plant sources. A very common toxin is the beta-aminopropionitrile present in lathyritic legumes, and another is the wildfire toxin (42) (Figure 21). 

Figure 21. Inhibition of glutamine synthetase by wildfire toxin (42)...

The first really molecular study of phytotoxins was done at the Rockefeller Institute, starting in the late 1940 s by a physiologist-biochemist team, Braun and Woolley, who worked with Pseudomonas syringae pv. tabaci. This bacterium produces the so called wildfire toxin, the name coming from the rapidity with which chlorosis is induced by the pathogen producing toxin in the leaves of the natural host, tobacco. They proposed a structure for this toxin, and because of its presumed structural and physiological resemblances to methionine sulfoximine, a recently discovered compound that interfered with methionine metabolism, they hypothesized that wildfire toxin acted in a similar, if not identical, manner. 

Perkins, G.L. and L. Lovrekovich Enzyme levels in tobacco leaf tissues affected by the Wildfire toxin Phytopathology 55 (1965) 519-524. 

It is noteworthy that a peptide produced by Pseudomonas tabacci has also been isolated and found to contain a monocyclic TV-substituted -lactam ring (238b) [206]. This compound is the wildfire toxin and the producing bacterium causes the wildfire disease of the tobacco plant. Later it was re-named... 

Tabtoxin or wildfire toxin (12), produced by Pseudomonas syringae pv. tabaci and related bacteria, on tobacco pro-... 

Wild-fire toxin is produced by Pseudomonas tabaci, an organism which causes a leafspot disease in tobacco plants. The correct structure was determined by Stewart (2), and shown to be (241), although no assignment of stereochemistry was made. Wild-fire toxin is an unstable substance rapidly converted at neutral pH to isotabtoxin (242) by way of intramolecular attack of the amino-group on the 3-lactam. Hydrolysis of wildfire toxin gives threonine and tabtoxinine (243). 

As the dipeptide J itself does not inhibit purified Glutamine synthetase in vitro [143], the amino acid K is considered to be the active form of J and hence, the actual toxin of wildfire disease. Since, the detailed mechanism of Glutamine synthetase inhibition by tabtoxinine-(3-lactam attracts chemical interest, a synthetic approach to the toxin K and its analogs, is of increasing importance. Spiro-(3-lactam L (Fig. 11) has been found to be an efficient precursor of toxin K. 

Tabtoxinine-/3-lactam (T/3L), a Tobacco Wildfire Disease Toxin. 204... 

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