The inactivation of rhodanese by nitrite and inhibition by other anions in vitro

Abstract

Cyanide detoxification in mammals occurs, in part, by sulfur transfer by rhodanese to form the less toxic thiocyanate. Thiosulfate and nitrite are often used in combination for the treatment of cyanide intoxication. This report shows that nitrite can inhibit the rate of sulfur transfer by rhodanese in vitro. Nitrate, chloride, sulfate, and acetate were also examined as inhibitors. Inhibition by nitrite appeared to be more complex than for the other anions tested. Closer examination showed that nitrite can inactivate the sulfur-free rhodanese. Our observation leads to the suggestion that, in vivo, either rhodanese is maintained in its more stable sulfur-substituted form or cellular compartmentalization prevents inactivation by nitrite.

The two faces of cyanide: an environmental toxin and a potential novel mammalian gasotransmitter

“…TST displays a catalytical efficiency in catabolizing cyanide in the order of 10 3 m −1 s −1 , with cyanide showing K M values of ∼ 30 m m , although polymorphic variants found in humans show a significant difference in sulfur transfer kinetics [ 246 ]. More recently, the role of TST in cyanide detoxification has been re‐evaluated because of its predominantly mitochondrial localization and relevant expression levels restricted to liver and kidney, thus leaving other tissue and organs more exposed to cyanide toxicity [ 247 , 248 , 249 ].…”

Immobilized rhodanese: Some aspects of anion inhibition kinetics and modulation by cations

“…In the same vein, values of 9.6 mM, and 3.5 mM were observed for IR. Previously, Alexander et al (13) suggested that the formation of the s-nitroso enzyme derivative between the nitrite ion and sulfyhydryl group of the enzyme is the most feasible mechanism of rhodanese inactivation.…”