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
Succinyl CoA is formed by all except ? 
Select and explain. 
A. Proline, B. Isoleucine, C. Methionine, D. Valine
A: Proline
Answer: A: Proline 
Explanation: Histidine, proline, glutamine, arginineGlutamatea a-ketoglutaratelsoleucine, methionine, valineSuccinyl CoATyrosine, phenylalanineFumarateTryptophanAlanine a PyruvateHydroxyproline, serine, cysteine, threonine, glycinePyruvate