FIG. 2.

GC/MS of TBDMS-derivatized l-cystathionine (A) and l-homolanthionine (B). The molecular ions have m/z values of 678 (cystathionine) and 692 (homolanthionine). The mass difference of 14 is due to the additional methylene group present in homolanthionine. Characteristic fragments at [M-15], [M-57], [M-85], and [M-302] typically found for TBDMS-derivatized compounds also exhibited a mass difference of 14. The ions at m/z 170, m/z 244, and m/z 272 are characteristic fragments of the homocysteine residue in both molecules. l-Cystathionine was applied as a pure compound, and l-homolanthionine was from a cell extract of C. glutamicum ATCC 13032 ΔmcbR.