cysteine-specific re agents

Mer cu ric chlo ride, p-chloromercuribenzoate and 5,5′-dithiobis(2-nitrobenzoic acid) ir re vers ibly in hib ited the ac tiv ity of Esch e richia coli glu ta mate de car box yl ase. Their sec ond or der rate con stants for in ac ti va tion are 0.463 μMmin, 0.034 μMmin, 0.018 μMmin, re spec tively. The char ac ter is tics of the in hi bi tion by the three thiol-group re agents sup ports the idea that cysteinyl res i dues at the bind ing sites for the co fac tor and/or the sub strate are im por tant for en zyme ac tiv ity in E. coli.