<prompt> Substrate level phosphorylation occur in step catalysed by which of the following enzyme in TCA cycle?Isocitrate dehydrogenaseMalate dehydrogenaseAconitaseSuccinate thiokinase  <response>: Succinate thiokinase is the enzyme that generates ATP directly by substrate-level phosphorylation. In Krebs cycle succinate thiokinase catalyze the conversion of Succinyl CoA into succinate. In this step GDP is phosphorylated to GTP. GTP can then be conveed to ATP by reacting with an ADP molecule. Substrate-level phosphorylation is a type of metabolism that results in the formation and creation of adenosine triphosphate ATP or guanosine triphosphate GTP by the direct transfer and donation of a phosphoryl P03 group to adenosine diphosphate ADP or guanosine diphosphate GDP from a phosphorylated reactive intermediate. In glycolysis substrate level phosphorylation occur in two steps: Conversion of 1,3 BPG to 3 Phosphoglycerate catalyzed by Phosphoglycerate kinase Conversion of Phosphoenolpyruvate to pyruvate catalyzed by Pyruvate kinase Ref: Textbook of Biochemistry By D M Vasudevan, 3rd Edition, Page 195 