Rennenberg H, Steinkamp R, Polle A
Z Naturforsch C Biosci. 1980 Sep-Oct;35(9-10):708-11. doi: 10.1515/znc-1980-9-1008.
During degradation of glutathione in tobacco suspension cultures substancial amounts of 5-oxo-proline are formed in vivo as well as in crude cell homogenates in vitro. The existance of a 5-oxo-prolinase that catalyzes the conversion of 5-oxo-proline to glutamic acid was demonstrated in tobacco cells, grown with glutathione as sole sulfur source.