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 this paper indicates that the cyclic derivative of cystathionine, 1,4-hexahydrothiazepine-3,5-dicarboxylic acid, here simply named cyclothionine, is a normal component of bovine brain. This finding together with the detection of the same compound in the urine of cystathioninuric patients (Kodama, H., Sasaki, K., Mikasa, H., Cavallini, D., and Ricci, G. (1984) J. Chromatogr. 311, 183-188) supports the conclusion that cystathionine, apart from its role in trans-sulfuration, is converted also into cyclic compounds whose biochemical significance is as yet unknown.
D. Cavallini, L. Pecci, R. Matarese
The Journal of biological chemistry