Figure 2: High energy collision dissociation (HCD) tandem mass spectrum of human recombinant KAT II treated with GSH and disulfiram.
Experiments were performed as detailed in the text. The tandem mass spectrum of KAT II, residues X-X, is consistent with the presence of an intramolecular disulfide bond between the two cysteine residues. Fragmentation of the disulfide-linked cysteines resulted in the loss or retention of the sulfur yielding a dehydroalanine (−33.98) and sulfide (31.97), respectively. The asterisk indicates fragment ions in which the sulfur remained on the first cysteine.