Publication: Mercaptopyruvate sulfurtransferase as a defense against cyanide toxication. Molecular properties and mode of detoxification
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Date
1999
Authors
Nagahara, N. ; Ito, T. ; Minami, M.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
In cyanide poisoning, metalloproteins and
carbonyl groups containing proteins are the main target
molecules of nucleophilic attack by cyanide. To defend
against this attack, cyanide is metabolized to less toxic
thiocyanate via transsulfuration. This reaction is
catalyzed by rhodanese and mercaptopyruvate sulfurtransferase
(MST). Rhodanese is a well characterized
mitochondrial enzyme. On the other hand, little was
known about MST because it was unstable and difficult
to purify. We first purified MST to homogeneity and
cloned MST cDNA from rat liver to characterize MST.
We also found that MST was an evolutionarily related
enzyme of rhodanese. MST and rhodanese are widely
distributed in rat tissues, and the kidney and liver
prominently contain these enzymes. Immunohistochemical
study revealed that MST is mainly distributed
in proximal tubular epithelia1 cells in the kidney,
pericentral hepatocytes in the liver, the perinuclear area
of myocardial cells in the heart, and glial cells in the
brain, and immunoelectron microscopical study
concluded that MST was distributed in both cytoplasm
and mitochondria, so that MST first detoxifies cyanide
in cytoplasm and the cyanide which escapes from
catalysis due to MST enters mitochondria. MST then
detoxifies cyanide again in cooperation with rhodanese
in mitochondria. Tissues other than the liver and kidney
arc more susceptible to cyanide toxicity because they
contain less MST and rhodanese. Even in the same
tissue, sensitivity to cyanide toxicity may differ
according to the kind of cell. It is determined by a
balance between the amount of proteins to be attacked
and that of enzymes to defend.
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