FIG 7.

Investigation of the reverse reaction of S-sulfocysteine and CysK2. (A) The UV-vis spectrum of CysK2 in the presence of 2 mM S-sulfocysteine results in fast enzyme-aminoacrylate intermediate formation (blue-gray). (B) The spontaneous formation and decay of the intermediate for the back reaction were monitored in the stopped-flow spectrophotometer, and pseudo-first-order rate constants (k_obs) were determined from exponential fits (insets) for the formation and the decay of the reaction intermediate.