α-ketoglutarate dehydrogenase (α-KGDH) is a key enzyme in the tricarboxylic acid (TCA) cycle. While the substrate being catalyzed by α-KGDH, NAD+ is reduced to NADH, and electrons are transfered to WST-8 under the action of hydrogen transmitter to produce yellow product. The activity of α-KGDH can be calculated by measuring the change of absorbance value at 450 nm