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A competitive inhibitor of succinic dehydrogenase is :
A
$\alpha$-ketoglutarate
B
malate
C
malonate
D
oxaloacetate
Detailed Solution
Succinic dehydrogenase is the Krebs cycle enzyme that converts succinate into fumarate.
A competitive inhibitor is a substance that closely resembles the substrate in its molecular structure and competes with it for the active site of the enzyme.
Malonate ($^-OOC-CH_2-COO^-$) is very similar in structure to succinate ($^-OOC-CH_2-CH_2-COO^-$); both are dicarboxylic acids.
Malonate binds to the active site of succinic dehydrogenase but cannot be dehydrogenated, so the substrate cannot bind and the enzyme action declines.
This inhibition can be overcome by increasing the concentration of the substrate (succinate), which is the characteristic feature of competitive inhibition.
$\alpha$-ketoglutarate, malate and oxaloacetate are intermediates of the Krebs cycle, not the classical competitive inhibitor of this enzyme.
So the competitive inhibitor of succinic dehydrogenase is malonate.
A competitive inhibitor is a substance that closely resembles the substrate in its molecular structure and competes with it for the active site of the enzyme.
Malonate ($^-OOC-CH_2-COO^-$) is very similar in structure to succinate ($^-OOC-CH_2-CH_2-COO^-$); both are dicarboxylic acids.
Malonate binds to the active site of succinic dehydrogenase but cannot be dehydrogenated, so the substrate cannot bind and the enzyme action declines.
This inhibition can be overcome by increasing the concentration of the substrate (succinate), which is the characteristic feature of competitive inhibition.
$\alpha$-ketoglutarate, malate and oxaloacetate are intermediates of the Krebs cycle, not the classical competitive inhibitor of this enzyme.
So the competitive inhibitor of succinic dehydrogenase is malonate.