Exam 3 Enzyme regulation

Question 1

cAMP dependent protein kinase

Answer 1

• functions in the mobilization of TAG’s from adipose tissue to use for energy
• phosphorylates hormone sensitive lipase, rendering it active
• activated by glucagon and epinephrine which creates cAMP inside the cell via adenylate cyclase

Question 2

hormone sensitive lipase

Answer 2

• active when phosphorylated
• phosphorylated by cAMP dependent kinase
• active when glucagon and epinephrine are present, as well as citrate and AMP
• converts TAG’s to FA’s in adipose tissue

Question 3

CAT1

Answer 3

• works in the cytoplasm of cells that are using fat as an energy source
• combines FA-CoA and carnitine to make FA-carnitine which is the transported into the mitochondria
• inhibitted by malonyl-CoA which is the product of the first comitted step to FA biosynthesis

Question 4

CAT2

Answer 4

-works inside the mitochondria to remove carnitine from FA and replace it with CoA

Question 5

Acetyl CoA carboxylase

Answer 5

• converts acetyl Coa to malonyl CoA, it is the first committed step in FA synthesis
• active when dephosphorylated, which allows it to be in a polymeric form
• activated by citrate and insulin which increase the activity of a phosphatase
• inhibitted by palmitoyl-CoA which is the product of fatty acid synthesis, malonyl CoA which is the product of the first committed step of FA synthesis, protein kinase, glucagon and epinephrine

Question 6

acyl transferase (FAS)

Answer 6

-transfers acetyl CoA to the ACP

Question 7

condensing enzyme and malonyl transferase (FAS)

Answer 7

-acetyl CoA is condensed with malonyl CoA

Question 8

beta keto reductase (FAS)

Answer 8

-converts a ketone on malonyl to an OH using NADPH

Question 9

dehydratase (FAS)

Answer 9

-Oxidizes the OH to create a double bond

Question 10

enoyl reducatse

Answer 10

• using NADPH reduces the double bond to a single bond, giving a FA butarate
• the process starts all over again after this, adding 2 C’s to the chain at a time

Question 11

elongases

Answer 11

• adds 2C to the carboxyl end with no change in omega number
• formation of the beta ketone can happen on the SER or in the mitochondria
• uses 2 NADPH

Question 12

desaturases

Answer 12

• adds cis double bonds
• never closer to the omega carbon then omega 7
• located on the membrane surface of the SER

Question 13

oxygenases

Answer 13

-oxidizes PUFA’s to make intracellular messengers

Question 14

hydroxylases

Answer 14

• adds OH to the alpha C of some FA’s

- important in the formation of myelin

Question 15

Glycerol phosphate dehydrogenase

Answer 15

• committed step in triglyceride synthesis

- converts DHAP (a glycolysis intermediate) into glycerol 3 phosphate

Question 16

Diacylglycerol acyltransferase

Answer 16

-converts diacylglycerol to triacylglycerol

Question 17

MGAT

Answer 17

-converts 2-MAG into diacylglycerol

Question 18

thiolase in keton body formation

Answer 18

• combines 2 acetyl CoA molecules to make acetoacetyl CoA

- in liver mitochondria

Question 19

HMG CoA synthase in ketone body formation

Answer 19

• uses acetoacetyl CoA and acetyl CoA to make HMG-CoA

- in liver mitochondria

Question 20

HMG CoA lyase in ketone body formation

Answer 20

• in liver mitochondria

- produces acetoacetate which can then be converted to beta hydroxy acetone phsosphate which is a keton body

Question 21

3 keto acyl transferase

Answer 21

• uses acetoacetate and succinyl CoA form the TCA cycle to make acetoacyl Coa and succinate
• acetoacyl coa is then converted to acetyl CoA by thiolase and used in the krebs cycle
• this is how cells use ketone bodies as energy
• this enzyme is not located in the liver because that is where ketone bodies are made to be used for the rest of the body, particularly the brain, and therefore the liver does not use ketone bodies as an energy source

Question 22

cytidil transferase

Answer 22

-creates a phospodiester bond in the formation on glycerophospholipids

Question 23

kinases role in the formation of glycerophospholipids

Answer 23

-it phosphorylates the alliphatic alchol to beign the process

Question 24

cyclooxygenase

Answer 24

• converts PUFA’s into prostaglandins and thromboxanes by adding 2 oxygens and removing two double bonds
• inhibited by aspirin
• these are omega 3 or omega 6 PUFA’s that are created by PLA2

Question 25

5-lipoxygenases

Answer 25

-act on PUFA’s created by PLA2 to make leukotrienes

Question 26

PLC

Answer 26

• signalling, cuts to give DAG and phosphorylated head group
• activated by a GPCR that has been activated by hormone or growth factor
• turns PIP2 into DAG (activation of PKC) and IP3 (Ca++ release, activates calmodulin kinase and PKC, promotes growth and development)

Question 27

PLD

Answer 27

-gives phosphatidic acid (DAG with a phosphate on C3) and a head group alc

Question 28

HMG CoA reductase

Answer 28

• first committed step in cholesterol synthesis
• uses HMG-CoA and NADPH to make melavonic acid
• inhibited by cholesterol in 3 ways: allosteric, increased degradation of enzyme, and decreased trancription
• inhibited by AMPK kinase via glucagon and epinephrine
• inhibited by statin drugs

Question 29

squalene monoxygenase

Answer 29

-uses NADPH, FPP, and squalene to make squalene epoxide (30C)

Question 30

increased cholesterol leads to

Answer 30

• decreased HMG-CoA reductase
• decreased LDL receptor in membranes
• increased ACAT

Question 31

7 alpha hydroxylase

Answer 31

• first step in the formation of bile salts

- converts cholesterol to 7-hydroxylcholesterol

Question 32

vitamin k dependent carboxylase

Answer 32

-uses vitamin K and the glutamate on prothrombin to crete gama carboxyglutamate on prothrombin