MetabolismLecture 6 - Fatty Acid Breakdown Flashcards
What are the 2 most important enzymes in the Fatty Acid Synthesis/Breakdown pathway?
What is their function?
- CPT1 (Carnitine Palmitoyl Transferase I)
- convert Fatty Acyl CO A’s into Acetyl Co A - Acetyl Co A Carboxylase
- convert Acetyl Co A into Fatty Acyl CO A
When are fatty acids mobilized from adipose tissue TAGs into the liver? By what enzyme?
NEED FOR ATP
HSTL
- hormone-senitive triacylglycerol lipase
What are the negative and positive hormonal regulators of HSTL?
negative = INSULIN
positive = EPINEPHRINE
- HSTL converts TAGS into glycerol for transport into the liver
What are the fates of Released fatty acids?
What are the fates of released Glycerol?
Released fatty acids
Enter the circulation
Bind to albumin
Are carried to muscle, liver, etc.
For beta-oxidation and energy production
- Released glycerol
Is transported to liver and kidney
Glycerol kinase phosphorylates glycerol to
glycerol 3-phosphate, which can be used in gluconeogenesis
What is the rate limiting enzyme in fatty acid biosynthesis?
What allosterically inhibits this enzyme in FA biosynthesis?
Acetyl Co A Carboxylase
- Fatty Acyl Co A’s (the starting material) can inhibit this enzyme
How much ATP does the complete oxidation of palmitate yield?
106 ATP
What is removed in each cycle of fatty acid degradation?
remove 2 carbon units
- FADH2, NADH and Acetyl Co A are produced
(8 Acetyl Co a, 7 NADH and 7 FADH2 are produced with the total oxidation of palmitate)
Where are ketone bodies formed?
Liver mitochondria
Acyl CO A from Free Fatty Acids from Acetyl Co A and Acyl Glycerol
What is the 1st ketone body?
What is the second ketone body?
- Acetoacetate
2. B-HydroxyButyrate and Acetone formed from Acetoacetate spontaneously
What is the rate limiting enzyme in Ketone Biosynthesis?
Where is it found?
What is the key enzyme for ketone utilization?
Where is it not found?
HMG - CoA Synthase
- FOUND ONLY IN THE LIVER
Acetoacetate: succinyl CoA Transferase enzyme
- NOT FOUND IN LIVER
What does Acetoacetate Succinyl Co A do?
Convert Acetoacetate into Acetoacetyl Co A
What tissues cannot use fatty acids as an energy source?
RBC Brain Nervous System Adrenal Medulla Lens
What transports long chain fatty acids into the MITOCHONDRIAL MATRIX for B-oxidation?
Inhibition results in ? (2)
Carnitine
- Inhibits Fatty Acid oxidation
- Decreases ATP production
What inhibits CPT1?
Malonyl Co A
- inhibits B-oxidation of fatty acids
(Malonyl Co A is the product of fatty acid biosynthesis)
Deficiency in which enzyme results in SIDS?
MCAD
- medium chain Fatty Acid CoA Dehydrogenase
Ketone bodies are synthesized from _____ in ____
- Acetyl CO A
2. Mitochodnria
What enzyme does the liver lack that prevents it from being able to USE ketone bodies?
What enzyme is present ONLY in the liver required for ketone biosynthesis?
THIOPRASE/ AcetoAcetate: SUccinyl CoA Transferase
HMG - CoA Synthase
What hormones promote the BREAKDOWN and inhibit breakdown of TAG (Triacylglycerol)
What enzyme is responsible for converting TAG into Free Fatty Acids (FFA)?
Insulin - inhibits breakdown
EPinephrine - promotes breakdown
- HST Lipase
Describe how Glucagon & Einephrine stimulate the following:
- Malonyl CO A
- Acetyl CO A Carboxylase
- CPT-1
- INHIBIT fatty acid synthesis
- INHIBIT
- Stimulate - involved in formation of ketone bodies
What is the only known inhibitor of CPT-1
Malonyl Co A
-, the product of fatty acid biosynthesis?
Define the following for Acetyl - Co A Carboxylase:
- Activator
- Inhibitor
- Hormonal Activator
- Hormonal Inhibitor
- Induces synthesis
- Represses Enzyme synthesis
Comments?
Define the following for Acetyl - Co A Carboxylase:
- Activator - CITRATE
- Inhibitor - Long Chain Fatty Acyl Co A
- Hormonal Activator - INSULIN
- Hormonal Inhibitor - Glucagon/Epinephrine
- Induces synthesis - High carb diet, fat free diet
- Represses Enzyme synthesis - glucagon, epinephrine, high fat diet, fasting
Comments?
- REQUIRES BIOTIN,
synthesizes Malonyl Co A –> the inhibitor of CPT-1 (which converts fatty acyl into acetyl co A)
What is the only known inhibitor of CPT -1?
Malonyl Co A
- CPT -1 is active unless Malonyl Co A is present
What is the hormonal activator & inhibitor of HSTL?
2 for each
Activate:
- Epinephrine
- ACTH
Inhibit:
- insulin
- PGE
What are the following 2 enzymes involved with?
- Mitochondrial HMG - Co A
- Acetoacetate: Succinyl CO A Transferase
Where is each found?
- Mitochondrial HMG - Co A - LIVER
- FORMS KETONE BODIES - Acetoacetate: Succinyl CO A Transferase - NOT LIVER
- degrades Ketone Bodies
Where is each found?
