25 - Oxidation of fatty acids: β-oxidation of fatty acids with odd- and even number of carbon atoms. Carnitine shuttle. Energy balance. Regulation.

sections

• activation of FA

• regulation

• enzyme defects

• beta oxidation even and odd number

• canitine shuttle

• energy yield

• oral box

• activation of FA

• regulation

• Inhibited by malonyl-CoA (blocks CPT-I)

• Stimulated by fasting, glucagon, epinephrine

• Inhibited by insulin and high ATP/acetyl-CoA

• enzyme defects

• deficiency of hepatic CPT1 - decrease oxidation of fatty acid in liver → hypoglycaemia, decreased ketogenesis

• Deficiency in muscle CPT2 - muscle pain and fatigue and myoglobinuria

• beta oxidation even and odd number

• Occurs in mitochondria

• Even-numbered FAs → broken into acetyl-CoA units

• Odd-numbered FAs → last 3 carbons form propionyl-CoA → converted to succinyl-CoA (enters TCA cycle)

• carnitine shuttle

• Needed to transport long-chain fatty acids into mitochondria

• Steps:

  1. Fatty acyl-CoA → Fatty acyl-carnitine (CPT-I)

  2. Transport across inner membrane

  3. Reconversion to fatty acyl-CoA (CPT-II)

• energy yield

Example: Palmitate (C16) → 106 ATP
(via 7 cycles: 8 acetyl-CoA, 7 NADH, 7 FADH₂)

• oral box