This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Sulfur of cysteineare not used/ utilized in the body for the following process/product 
Select and explain. 
A. Help in the conversion of cyanide to thiocyanate, B. Thiosulfate formation, C. Introduction of sulphur in methionine, D. Disulfide bond formation between two adjacent peptide.
C: Introduction of sulphur in methionine
Answer: C: Introduction of sulphur in methionine 
Explanation: Methionine is an essential amino acid, so it cannot besynthesized from Cysteine.- But Sulfur of cysteine is donated by sulfur ofmethionine.- This is called transsulfuration reaction.- PLP is the coenzyme of transrulfuration.- The reaction is catalyzed by Cystathionine betaSynthase and Cystathionase enzyme