title: On the reactivity of metallothioneins with 5,5'-dithiobis-(2-nitrobenzoic acid).
abstract: Rat liver and horse kidney metallothioneins react with 5,5'-dithiobis-(2-nitrobenzoic acid) (Nbs2) to release 5-thio-2-nitrobenzoate and metal ions. The reactions are slow and exhibit biphasic kinetics with each process having an empirical rate law of the form: rate - k[RSM] X [Nbs2] + k'[RSM], where RSM represents mental-bound thiolate groups. The pseudo-first-order rates are insensitive to pH but are modified in guanidine hydrochloride solution. Rat liver metallothioneins of variable zinc, copper and cadmium composition react similarly and give observable thiol/total metal ratios in good agreement with stoichiometries of SH/(Cd + Zn) of 3 and SH/Cu of 1. A model complex cadmium-2,3-dimercaptopropanol, resembles the proteins in its reaction with Nbs2.
mesh_terms: D000818:Animals; D001665:Binding Sites; D004112:Dimercaprol / Q000378:metabolism; D004228:Dithionitrobenzoic Acid / Q000378:metabolism*; D006736:Horses; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008667:Metalloproteins / Q000378:metabolism*; D008668:Metallothionein / Q000378:metabolism*; D009579:Nitrobenzoates / Q000378:metabolism*; D051381:Rats
chemical_list: D008667:Metalloproteins; D009579:Nitrobenzoates; D004112:Dimercaprol; D008668:Metallothionein; D004228:Dithionitrobenzoic Acid