Which of the following enzymes catalyzes a reaction of the citric acid cycle that does NOT produce reduced electron carriers?

A) Malate dehydrogenase

B) Succinate dehydrogenase

C) Succinyl CoA synthetase

D) α-ketoglutarate dehydrogenase

E) Isocitrate dehydrogenase

C) Succinyl CoA synthetase

Explanation:

Malate dehydrogenase converts L-Malate and NAD⁺ to Oxaloacetate, NADH and H⁺. Reduced electron carrier - NADH is produced.

Succinate dehydrogenase converts succinate and FAD to fumarate and FADH₂. Reduced electron carrier - FADH₂ is produced.

α-ketoglutarate dehydrogenase converts α-Ketoglutarate, NAD⁺ and CoA-SH to Succinyl-CoA, NADH, H⁺ and CO₂. Reduced electron carrier - NADH is produced.

Isocitrate dehydrogenase converts Isocitrate and NAD⁺ to α-Ketoglutarate, NADH, H⁺ and CO₂. Reduced electron carrier - NADH is produced.

But on the other hand, Succinyl CoA synthetase Succinyl-CoA, GDP and Pi to Succinate, CoA-SH and GTP and thus no reduced electron carrier is produced.