Lipids IV Flashcards
What are sphingolipidoses?
rare genetic disease
results in accumulation of undegraded glycolipids in the lysosomes of phagocytic cells
What enzymatic defect is present in Tay-Sachs? What is the accumulated lipid?
beta-hexosaminidase.
ganglioside
What enzymatic defect is present in Gaucher’s? What is the accumulated lipid?
beta-glucosidase or beta-cerebrosideas
GLUCOcerebroside
What enzymatic defect is present in Fabry’s? What is the accumulated lipid?
alpha-galactosidase
ceramide trihexoside
What enzymatic defect is present in Niemann-Pick? What is the accumulated lipid?
sphingomyelinase
sphingomyelin
What enzymatic defect is present in Sandhoff Disease? What is the accumulated lipid?
beta-hexosaminidase A and B
gangliosides and globosides
Metachromatic leukodystrophy
arylsulfatase
sulfatide
What is the presentation of Gaucher’s Disease?
liver and spleen enlargement, erosion of long bones
Where does the formation of ketone bodies occur? Where does the synthesis of cholesterol occur?
ketone bodies = mitochondria
cholesterol = cytosol
When do the formation of ketone bodies and cholesterol diverge?
at the function of HMG-CoA Synthase
What is the rate limiting step for the production of cholesterol?
HMG-CoA Reductase
What does HMG-CoA Reductase produce? What does it use for a reducing equivalent?
mevalonic acid.
NADPH
How is HMG-CoA Reductase regulated?
AMP-dependent kinase inactivates the enzyme
HMG-CoA Reductase is active when cellular energy is high
How is HMG-CoA Reductase regulated hormonally?
Insulin dependent dephosphorylation activates the enzyme
Does HMG-CoA Reductase experience end-product inhibition?
yes.
What is the function of lecitin:cholesterol acyltransferase (LCAT)?
to esterify a long-chain acyl group to the C3 of cholesterol
Where are cholesteryl esters found?
hydrophobic center of lipoproteins or fat droplets
What three things need to happen to cholesterol in order to become a bile acid?
oxidation of C24
hydroxylation of C7 and C12
Where does the liver synthesize and secrete bile acids?
the intestine
Where does cholesterol synthesis take place? Where does ketone body synthesis take place?
cholesterol = cytosol
ketone body = mitochondria
What mechanism separates ketone body synthesis from cholesterol synthesis?
HMG-CoA Synthase isoforms
What is the rate limiting step for cholesterol synthesis?
HMG-CoA Reductase
What carbon # of cholesterol is esterified ?
number 3
What enzyme esterifies cholesterol?
LCAT
