Detoxification of Cyanide by Thiosulfate Sulfotransferase: Physiology and Mechanism

The video tutorial explores the enzyme rhodanese, also known as thiosulfate sulfotransferase, which performs two main functions: biosynthesis of thiosulfate and detoxification of hydrogen cyanide. The enzyme's mechanism involves thioredoxin dependency and active site interactions with arginine residues. The process results in the formation of thiocyanate, which is excreted from the body. The tutorial provides a detailed explanation of the enzyme's role in detoxifying cyanide and the biochemical pathways involved.

What is the primary function of the enzyme rhodanese?

• To synthesize proteins

• To produce energy

• To detoxify hydrogen cyanide and synthesize thiosulfate

• To break down carbohydrates

Which of the following is NOT a function of rhodanese?

• Reacting with anionic cyanide

• Detoxifying hydrogen cyanide

• Synthesizing thiosulfate

• Breaking down proteins

What is the structural difference between thiosulfate and sulfate?

• Thiosulfate has an extra oxygen atom

• Thiosulfate has a sulfur atom replacing an oxygen atom

• Thiosulfate has a nitrogen atom

• Thiosulfate has a carbon atom

Which molecule is critical for the biosynthesis of thiosulfate?

• Vitamin B12

• Myoglobin

• Hemoglobin

• Thioredoxin

What is the role of thioredoxin in the biosynthesis of thiosulfate?

• It acts as a reducing agent

• It acts as an oxidizing agent

• It binds to cyanide

• It provides energy

How does rhodanese detoxify hydrogen cyanide?

• By converting it into water

• By binding it to oxygen

• By converting it into thiocyanate

• By breaking it down into carbon dioxide

What role do arginine residues play in the active site of rhodanese?

• They stabilize the enzyme structure

• They act as Bronsted-Lowry acids and bases

• They bind to hydrogen cyanide

• They provide energy for the reaction

What unusual feature is observed in the active site of rhodanese?

• Presence of a metal ion

• Nucleophilic attack on a negatively charged atom

• Formation of a covalent bond with oxygen

• Binding of a water molecule

What is the final product of the detoxification process catalyzed by rhodanese?

• Sulfate

• Thiosulfate

• Cyanide

• Thiocyanate

What happens to thiocyanate after it is formed?

• It binds to hemoglobin

• It is converted back to cyanide

• It is excreted from the body

• It is used in energy production