Which substrate is NOT a gluconeogenic precursor?

In gluconeogenesis, certain substrates are utilized to generate glucose, particularly during times when glucose stores are low, such as fasting. The substrates that can serve as precursors in gluconeogenesis include lactate, glycerol, and certain amino acids, but not all compounds contribute to this metabolic pathway.

Glycerol can be converted into dihydroxyacetone phosphate (DHAP), an intermediate of gluconeogenesis, making it a gluconeogenic precursor. Similarly, lactate can be converted back to pyruvate through the enzyme lactate dehydrogenase, which can then enter gluconeogenesis to eventually form glucose.

Alpha-ketoglutarate is an intermediate in the Krebs cycle and can also be converted into glucose through gluconeogenesis by being transformed into succinyl-CoA and then participating in various pathways leading to glucose synthesis.

However, acetyl-CoA is a critical metabolic intermediate that plays a key role in energy production and biosynthesis, especially in the citric acid cycle and fatty acid synthesis. Importantly, acetyl-CoA cannot be converted into pyruvate, and therefore cannot directly participate in gluconeogenesis. The entry point of the gluconeogenic pathway hinges on the conversion of pyruvate