This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzymes, Subject name: Biochemistry
[{'content': 'Substrate level phosphorylation is seen in reaction catalyzed by which enzyme of citric acid cycle? \nSelect and explain. \nA. Pyruvate kinase, B. Succinate thiokinase, C. Phosphoglycerate kinase, D. All of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The 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, Page no: 218', 'role': 'assistant'}]