Fatty acid catabolism
1. Digestion, Mobilization, and Transport
of Fatty acids
2. b Oxidation
3. Ketone Bodies
Digestion of dietary lipids in vertebrates
glucagon
Mobilization of
triacylglycerols
stored in
adipose tissue
β Oxidation of fatty acids-the free fatty acids that enter the cytosol
from the blood cannot pass directly through the mitochondrial membranes
1. Acyl-CoA synthetases :
Fatty acid +CoA + ATP
→ fatty acyl-CoA + AMP + PPi
isozymes for short,
intermediate, or long chainfatty acids
2. Carnitine acyl transferase I - acyl-carnitine/carnitine
transporter - carnitine acyltransferase II:
Complete
oxidation of fatty
acids into CO2
and ATPβ oxidation,
TCA cycle,
electron transport chain
LCAD C 12-18
MCAD C 4-14
SCAD C to 8
(AD)
The βoxidation of
palmitoyl CoA
Genetic mutation
of MCAD causes
serious diseases
Palmitoyl-CoA + 7 CoA + 7 FAD + 7 NAD+ + 7 H2O
8 actyl-CoA + 7 FADH2 + 7 NADH + 7 H+
Coordinated regulation of fatty acid synthesis
and oxidation
[NADH]/[NAD+]
[Acetyl-CoA]
Ketone Bodies - formed
in the liver and oxidized in skeletal
and heart muscle and the renal
cortex. Brain adapts to use them
under starvation conditions
Ketone body formation
in liver
in mitochondria
matrix
in cytosol for
cholesterol
synthesis
Ketone body oxidation
Extrahepatic
tissue
Untreated diabetes,
severe dieting, fasting
promote
gluconeogenesis, slow
the citric cycle (by
drawing off oxaloacetate)
and enhance the
conversion of acetylCoA to acetoacetate.
• Ketone bodies in the blood and urine of
untreated diabetics can reach extraordinary
levels, a condition called ketosis.
• In individuals on every low-calorie diets, using
the fats stored in adipose tissue as their
major energy source, levels of ketone bodies
in the blood and urine must be monitored to
avoid the dangers of acidosis and ketosis
(ketoacidosis).