Lipoprotein

Question 1

APOC2 activates what enzyme?

Answer 1

LPLase

Question 2

ApoA activates what enzyme?

Answer 2

LCAT

Question 3

Hepatic SR-B1 removes what?

Answer 3

• removes mature HDL from circulation
• binds HDL particles with high affinity
• not down-regulated by high intracell cholesterol levels
• expressed in liver & steroidogenic tissues (adrenal glands & gonads)
• SR-B1 also transports LCFA (has FA translocase properties)

Question 4

Paraoxonase activity on oxLDL

Answer 4

• inhibits oxidative mod of LDL
• transported in plasma as component of HDL

Question 5

LCAT fx?

Answer 5

• transfers a FA from PtdCho (C-2 lecithin) to cholesterol (C-3) by Entrapment
• Cholesteryl esters, now totally hydrophobic, accumulate in the interior of the HDL particle.
• LCAT activation require interaction of Apo-A1 (synthesized by enterocytes and hepatocytes)
• reduces free cholesterol levels
• regulates composition of plasma lipoproteins & indirectly cholesterol content of membranes

Question 6

ACAT fx

Answer 6

• Acyl CoA: cholesterol acyltransferase (cytoplasmic) synthesises cholesteryl esters from free cholesterol on cytoplasmic face of ER

Question 7

Apo-A1: sites of synthesis & fx

Answer 7

• sites of synthesis: intestines & liver
• activates LCAT
• structural in HDL

Question 8

Apo-A2: sites of synthesis & fx

Answer 8

• sites of synthesis: Intestines & liver
• fx: activator of hepatic lipase

Question 9

Apo-B100: sites of synthesis & fx

Answer 9

• sites of synthesis: liver
• fx: structural (in LDL & VLDL) & receptor binding

Question 10

Apo-B48: sites of synthesis & fx

Answer 10

• sites of synthesis: intestines
• fx: structural (in chylomicrons)

Question 11

Apo-C1: sites of synthesis & fx

Answer 11

• sites of synthesis: liver
• fx: possible cofactor for LCAT

Question 12

Apo-C2: sites of synthesis & fx

Answer 12

• sites of synthesis: liver
• fx: activator of LPLase

Question 13

Apo-C3: sites of synthesis & fx

Answer 13

• sites of synthesis: liver
• fx: possible inhibitor of LPLase

Question 14

ApoE: sites of synthesis & fx

Answer 14

• sites of synthesis: liver & intestines
• fx: receptor binding