biochem pathway query

[coreytayloris]

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in kaplan, they state that

"the acetyl co-a from beta oxidation enters the citric acid cycle in muscle.

in the liver, the acetyl-co a produced from beta oxidation (which cannot be converted to glucose) stimulates gluconeogenesis."

the underlined point confuses me, acetyl-co a isn't directly forming glucose but in essence it is indirectly forming glucose by stimulating pyruvate carboxylase, and thus gluconeogenesis???

 

[VCorp]

yup, because it's an obligate activator of the enzyme PCarboxylase.

 

[Pharmdmba1978]

in kaplan, they state that

"the acetyl co-a from beta oxidation enters the citric acid cycle in muscle.

in the liver, the acetyl-co a produced from beta oxidation (which cannot be converted to glucose) stimulates gluconeogenesis."

the underlined point confuses me, acetyl-co a isn't directly forming glucose but in essence it is indirectly forming glucose by stimulating pyruvate carboxylase, and thus gluconeogenesis???

That is correct, beta oxidation of ketone bodies and even chain fatty acids cannot directly be used to form glucose. Beta oxidation of even chain fatty acids and ketone bodies produces acetyl-co a. The 2 carbon acetyl-co a produced by beta oxidation of even chain fatty acids and ketone bodies is lost by the time the TCA cycle reaches succinyl-CoA. Therefore, the 2 carbons that were produced as acetyl-co a cannot contribute directly to gluconeogenesis. However, acetyl-co a stimulates pyruvate carboxylase which increases the formation of oxaloacetate which can be used for gluconeogenesis.

Hope that helps.