Rhodanese is a mitochondrial enzyme that handles sulfur reactions. Rhodanese detoxifies cyanide (CN-) by addition of a sulfur to form thiocyanate.
Carnivorous animals express rhodanese, which suggests that cyanide can be produced in tissues and is not only obtained from plant diets. Cyanide poisons mitochondrial respiration by binding and inhibiting the cytochromes.
It's possible that biogenic cyanide contributes to the "respiratory defect" that Otto Warburg showed characterizes all cancers studied.
Providing thiosulfate to the rhodanese system can improve the rate of detoxification of cyanide.
Source: Ray Peat's Newsletter, A New Approach to Detoxifying. Townsend Letter for Doctors January 1989 (Link)