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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.

SUBMITTER: Li TY

PROVIDER: S-EPMC1162625 | biostudies-other | 1981 Feb

REPOSITORIES: biostudies-other

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Inhibition of the condensing component of chicken liver fatty acid synthase by iodoacetamide and 5,5'-dithiobis-(2-nitrobenzoic acid).

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A marked gradation in active-centre properties in the cysteine proteinases revealed by neutral and anionic reactivity probes. Reactivity characteristics of the thiol groups of actinidin, ficin, papain and papaya peptidase A towards 4,4'-dipyridyl disulphide and 5,5'-dithiobis-(2-nitrobenzoate) dianion.

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