In energy stress, which enzyme is activated by a high AMP/ATP ratio to promote catabolic pathways?

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Multiple Choice

In energy stress, which enzyme is activated by a high AMP/ATP ratio to promote catabolic pathways?

When cellular energy is low, AMP rises relative to ATP, signaling a need to generate ATP. This increase activates AMPK, the cell’s main energy-sensing enzyme. AMP binds to AMPK, causing allosteric activation and promoting phosphorylation at Thr172 by upstream kinases (like LKB1). AMP binding also protects AMPK from dephosphorylation, so it stays active during energy stress. Once active, AMPK shifts metabolism toward ATP production: it enhances fatty acid oxidation by inhibiting acetyl-CoA carboxylase (reducing malonyl-CoA and freeing CPT1), and it promotes glycolysis and glucose uptake to supply energy. At the same time, it dampens energy-consuming anabolic processes such as lipid, protein, and cholesterol synthesis (e.g., inhibits ACC and mTORC1). The other enzymes listed are regulated by energy status in specific ways, but AMPK is the key regulator that directly senses the high AMP/ATP ratio and coordinates the broad switch to catabolic, ATP-generating pathways.

When cellular energy is low, AMP rises relative to ATP, signaling a need to generate ATP. This increase activates AMPK, the cell’s main energy-sensing enzyme. AMP binds to AMPK, causing allosteric activation and promoting phosphorylation at Thr172 by upstream kinases (like LKB1). AMP binding also protects AMPK from dephosphorylation, so it stays active during energy stress. Once active, AMPK shifts metabolism toward ATP production: it enhances fatty acid oxidation by inhibiting acetyl-CoA carboxylase (reducing malonyl-CoA and freeing CPT1), and it promotes glycolysis and glucose uptake to supply energy. At the same time, it dampens energy-consuming anabolic processes such as lipid, protein, and cholesterol synthesis (e.g., inhibits ACC and mTORC1). The other enzymes listed are regulated by energy status in specific ways, but AMPK is the key regulator that directly senses the high AMP/ATP ratio and coordinates the broad switch to catabolic, ATP-generating pathways.

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