We have synthesized a series of 4-substituted-2-nitrobenzene-sulfonyl compounds for caged fluorogenic probes and conducted a Hammett plot analysis using the steady-state kinetic parameters. The results revealed that the glutathione transferase (GST) alpha catalyzed reaction was dependent on the sigma value in the same way as the non-enzymatic reaction, whereas the dependence of the sigma value of the GST mu and pi was not as pronounced as that of GST alpha.