A defect in lactate dehydrogenase would require the coupling of which enzyme reaction to that of glyceraldehyde-3-phosphate dehydrogenase in order for effective gluconeogenesis to proceed?
A) glucose-6-phosphate dehydrogenase
B) malate dehydrogenase
C) PEP carboxykinase
D) pyruvate carboxylase
E) pyruvate dehydrogenase

Question

Quizplus · Accepted Answer

Malate dehydrogenase is involved in the conversion of oxaloacetate to malate in the mitochondria and back to oxaloacetate in the cytosol, which is necessary for gluconeogenesis when lactate dehydrogenase is defective.  In order for gluconeogenesis to occur, the NADH needed by the reversal of the glycolytic glyceraldehyde-3-phosphate dehydrogenase reaction must be supplied by either lactate dehydrogenase or the action of cytosolic malate dehydrogenase. In the latter reaction, the enzyme participates in the malate-aspartate shuttle.

A Defect in Lactate Dehydrogenase Would Require the Coupling of Which