Flashcards in Cholesterol Deck (14)
What is mevalonate?
An intermediate in cholesterol synthesis
What is the enzyme that catalyzes the reaction forming mevalonate?
Formed in a reaction catalyzed by HMG- CoA reductase
What is the rate limiting enzyme in cholesterol biosynthesis?
HMG- CoA reductase
What is squalene?
It is converted to lanosterol which is then converted to cholesterol
What activates HMG- CoA reductase?
What inhibits HMG- CoA reductase?
High cholesterol levels
How is HMG- CoA reductase regulated at the transcriptional level?
Inhibited by sterols like cholesterol
How is HMG- CoA reductase regulated at the translational level?
Inhibited by non sterol metabolites derived from mevalonate
How is HMG- CoA reductase regulated at the enzyme level?
Degradation is promoted by it s products, mevalonate and cholesterol
How is HMG- CoA reductase regulated at the activity level?
Phosphorylation inhibits like via AMP and glucagon
What is the rate limiting enzyme in bile acid synthesis?
What is the function of acyl-CoA cholesterol acyl-transferase (ACAT)?
Converts cholesterol to cholesterol ester
What is the effect of increased levels of cholesterol on enzymes in the pathway?
- Inhibits HMG-CoA reductase (decreased cholesterol synthesis)
- Activates ACAT
(increased cholesterol storage/utilization)
- Activates 7-a-hydroxylase
(increased bile acid synthesis/utilization)