During fasting, which enzyme of gluconeogenesis is transcriptionally upregulated by glucagon via CREB-mediated gene expression, and simultaneously post-translationally activated by acetyl-CoA?

• A Pyruvate carboxylase ✓
• B Phosphoenolpyruvate carboxykinase (PEPCK)
• C Fructose-1,6-bisphosphatase
• D Glucose-6-phosphatase

Explanation

Pyruvate carboxylase (PC) is the first committed step of gluconeogenesis, converting pyruvate → OAA. It requires biotin as cofactor. Crucially, PC is allosterically activated by acetyl-CoA — high acetyl-CoA (from fatty acid oxidation during fasting) signals that energy is available and gluconeogenesis can proceed. PC gene expression is also induced via cAMP/CREB during glucagon signaling. PEPCK is the next step and is also glucagon-induced, but its post-translational activation is by deacetylation, not by acetyl-CoA.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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