35. beta oxidation Flashcards
removal of acetyl CoA from the ends of fatty acids
beta-oxidation
products of beta-oxidation
- 8 Acetyl CoA -> citric acid cycle
- 7 NADH -> ETC
- 7 FADH2 -> ETC
where does beta oxidation occur
muscle
liver
•mitochondria
•fatty acid activation occurs in the cytosol
substrate of beta-oxidation
palmitate
rate limiting step in beta oxidation
translocation of fatty acyl coa from cytosol to the mitochondria
Enz : carnitine-palmitoyl transferase
Transport of fatty acyl coa to the mitochondria involves
- activation of the fatty acid ≈ fatty acyl synthetase
- attachment of fatty acyl to carnitine in the outer mitochondrial membrane ≈ carnitine acyltransferase-1
- fatty acyl-carnitine is shuttled through the inner membrane
- transfer of fatty acyl group back to a CoA in mitochondrial matrix
≈ carnitine acyltransferase-2
this enzyme activates the fatty acid
fatty acyl synthetase
degradation of faty acyl coa are a sequence of these steps, repeated 7 times
Oxidation —> Hydration —> Oxidation —> Thiolysis
OHOT
enzymes collectively known as fatty acid oxidase
(4) •fatty acyl coa dehydrogenase •∆2 enol coa hydratase •3-hydroxyacyl coa dehydrogenase •thiolase
how much ATP in NADH
2.5 ATP each
how much ATP in FADH2
1.5 ATP each
how much ATP in acetyl coa
10 ATP each
Net atp yield of palmitate
108 ATP -2 ATP (activation)
= 106 ATP
oxidize very long chains of fatty acids (C20, C22)
peroxisomes
oxidation of unsaturated FAs require this additional enzyme
3,2 enoyl-CoA isomerase
oxidation of FA with an odd number of carbon atoms will yield
acetyl Coa and a molecule of propionyl CoA
propionyl CoA is converted to ____, a TCA intermediate
succinyl CoA
propionyl CoA carboxylase requires
biotin
methylmalonyl CoA mutase requires
vit B12
rate limiting enzyme of lipogenesis
acetyl CoA carboxylase
subcellular location of lipogenesis
cytosol
subcellular location of beta oxidation
mitochondria
transport mechanism of lipogenesis
citrate shuttle
transport mechanism of beta-oxidation
carnitine shuttle
repetitive steps of lipogenesis
- condensation
- reduction
- dehydration
- reduction
CRDR
product of lipogenesis
palmitate
product of beta oxidation
8 acetyl CoA
7 NADH
7FADH2
activator of lipogenesis
citrate
inhibitor of lipogenesis
long-chain fatty acetyl CoA
inhibitor of beta oxidation
malonyl coa
hormonal state favoring lipogenesis
high insulin
hormonal state favoring beta -oxidation
high glucagon
lipid malabsorption manifests as
steatorrhea
lipid malabsorption results to
fat soluble vitamin and essential fatty acids deficiency
possible causes of lipid malabsorption
liver disease pancreatic disease cholelithiasis shortened bowel intestinal mucosal defects
deficiency of essential FA results in
ichthyosis (scaly dermatitis) hair loss poor wound healing visual neurologic abnormalities
carnitine deficiency causes
preterm infants liver disease malnutrition or strictly vegetarian diet pregnancy severe infections burns trauma hemodialysis
presents with
•hypoglycemia due to impaired fatty acid oxidation
•lipid accumulation with muscular weakness
carnitine deficiency
tx of carnitine deficiency
oral supplementation with carnitine
carnitine-palmitoyl transferase I deficiency affects the
liver
carnitine-palmitoyl transferase II deficiency affects the
cardiac and skeletal muscle
-cardiomyopathy, muscle weakness with myoglobinemia after prolonged exercise
leads to dec oxidation of FAs with 6-10 carbons
MCAD deficiency
medium chain fatty acyl coa dehydrogenase deficiency
most common inborn eror ofFA oxidation
MCAD deficiency
medium chain fatty acyl coa dehydrogenase deficiency
inheritance pattern of MCAD deficiency
autosomal recessive
MCAD deficiency
higher indcidence in
norther europeans
can manifest as
severe hypoglycemia
accumulation of FA in urine
sudden infant death syndrome
MCAD deficiency
medium chain fatty acyl coa dehydrogenase deficiency
tx of MCAD deficiency
- avoidance of fastig
2. IV glucose during acute episodes
caused by eating unripe fruit of the akee tree
jamaican vomiting sickness
toxin causing jamaican vomiting sickness
hypoglycin
hypoglycin inactives
medium and short chain acyl CoA dehydrogenase - inhibit beta oxidation
this disease is caused by deficiency of phytanoyl hydroxylase that leads to accumulation of phytanic acid
Refsum disease
Tx of refsum disease
diet low in phytanic acid
avoid dairy products, ruminant fat and meat
- presents with neurodegeneration (initial apathy and behavioral change, visual loss, spasticity, ataxia)
- adrenocortical insufficiecy
- hypogonadism
Adrenoleukodystrophy (ALD)
presents with
•liver dysfunction w/ jaundice
•marked mental retardation, weakness, hypotonia
•cranofacial dysmorphism - high forehead, shallow orbits, hypertelorism, high arched palate, abnormal helices of ears, retrognathia
•early death
zellweger syndrome
- peripheral neuropathy and ataxia
- retinitis pigmentosa
- abnormalities in skin and bones
refsum disease
- cerebrohepatorenal syndrome
- inherited absences of peroxisomes in all tissues
- marked accumulation of very long chain, saturated, unbranched, fatty acids in the liver, and central nervous system
Zellwegger syndrome
inability to transport VLCFAs across the peroxisomal membrane leads to accumulation in the brain, adrenals and testes
adrenoleukodystrophy
tx of ALD
Adrenoleukodystrophy
Adrenal hormone replacement therapy
Hematopoetic stem cell transplantation