In the Krebs cycle, Malonate competitively inhibits: (A) Isocitrate dehydrogenase, (B) Succinate thiokinase, (C) Succinate dehydrogenase, (D) a-Ketoglutarate dehydrogenase
Answer is C. The first dehydrogenation reaction, forming fumarate, is catalyzed by succinate dehydrogenase, which is bound to the inner surface of the inner mitochondrial membrane. The enzyme contains FAD and iron-sulfur (Fe-S) protein, and directly reduces ubiquinone in the electron transpo chain. This is inhibited by Malonate Reference: Harper; 30th edition; Page no: 163