Cystathionine has been reported to undergo enzymatic changes leading to the formation of seven membered cyclic products (Ricci, G., Santoro, L., Achilli, M., Matarese, R. M., Nardini, M., and Cavallini, D. (1983) J. Biol. Chem. 258, 10511-10517; Cavallini, D., Costa, M., Pensa, B., and Coccia, R. (1985) Biochem. Int. 10, 641-646). Gas-chromatographic and mass-spectrometric evidence reported in...