This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory chain, Subject name: Biochemistry
Substrate-level phosphorylation seen in reaction catalysed in 
Select and explain. 
A. Succinate dehydrogenase, B. Alfa-ketoglutarate dehydrogenase, C. Succinyl CoA thiokinase, D. Malate dehydrogenase
C: Succinyl CoA thiokinase
Answer: C: Succinyl CoA thiokinase 
Explanation: 5th Step of TAC CYCLE: Generation of Succinate The next reaction involves a substrate level phosphorylation whereby a high energy phosphate is generated from the energy trapped in the thioester bond of succinyl CoA. The enzyme is succinate thiokinase (step 5, Fig.18.2). A molecule of GDP is phosphorylated to GTP and succinate is formed. The GTP can be conveed to ATP by reacting with an ADP molecule: GTP + ADP - GDP + ATPRef: DM Vasudevan Textbook of Medical Biochemistry, 6th edition, page no: 218