Do Antidotes for Acute Cyanide Poisoning Act on Mercaptopyruvate Sulfurtransferase to Facilitate Detoxification?
Noriyuki Nagahara , Qing Li and Nori Sawada A well-known combined therapy for acute cyanide poisoning is intravenous administration of sodium nitrite, sodium thiosulfate and cobalt EDTA. Sodium nitrite oxidizes oxy-hemoglobin, resulting in methemoglobin, which has a high affinity for cyanide. Sodium thiosulfate is a substrate of thiosulfate: cyanide sulfurtransferase (rhodanese, EC.2.8.1.1), and facilitates catalytic metabolism of cyanide to less toxic thiocyanate. Cobalt EDTA combines with cyanide to reduce cyanide in the blood. Here, we focus on cytosolic and mitochondrial mercaptopyruvate sulfurtransferase (MST, EC. 2.8.1.2), which detoxifies cyanide more effectively than rhodanese, because rhodanese is localized only in mitochondria. Thiosulfate also serves as a substrate of MST and cyanide can be metabolized to thiocyanate. However, the Km value for thiosulfate is so large that it is not expected to contribute much to the detoxification of cyanide. On the other hand, nitrite and c
