Fatty acid oxidation

Beta-oxidation

Metabolic process in mitochondria that breaks down fatty acids to acetyl-CoA, NADH, and FADH₂ for ATP production

Fatty acid activation

Conversion of fatty acid to fatty acyl-CoA using ATP by acyl-CoA synthetase

Carnitine shuttle

Transport system that moves long-chain fatty acyl-CoA into the mitochondrial matrix via CPT-I, translocase, and CPT-II

CPT-I

Enzyme on outer mitochondrial membrane that forms fatty acyl-carnitine; inhibited by malonyl-CoA

Mobilisation

Breakdown of triglycerides in adipose tissue into fatty acids and glycerol via hormone-sensitive lipases

Hormone-sensitive lipase

Enzyme activated by glucagon and epinephrine to release fatty acids from adipose tissue

Perilipin

Protein that reorganizes lipid droplets to allow lipase access during fat mobilisation

Albumin

Blood protein that transports free fatty acids in circulation

Fatty acid transport proteins (FATP)

Proteins that facilitate fatty acid entry into cells

Fatty acid binding proteins (FABP)

Intracellular proteins that transport fatty acids within cells

Beta-oxidation cycle

Four-step repeating process (oxidation, hydration, oxidation, thiolysis) that shortens fatty acids by 2 carbons

Acyl-CoA dehydrogenase

Enzyme that catalyzes first oxidation step producing FADH₂

Enoyl-CoA hydratase

Enzyme that hydrates double bond in beta-oxidation

β-hydroxyacyl-CoA dehydrogenase

Enzyme that produces NADH in second oxidation step

β-ketothiolase

Enzyme that cleaves acetyl-CoA from fatty acyl-CoA

Acetyl-CoA

Two-carbon unit produced from fatty acid breakdown that enters the TCA cycle

Palmitate oxidation

Complete breakdown of C16 fatty acid yielding 106 ATP net

Unsaturated fatty acid oxidation

Beta-oxidation requiring additional enzymes due to presence of double bonds

Enoyl-CoA isomerase

Enzyme that converts cis double bonds to trans form for continuation of beta-oxidation

2,4-dienoyl-CoA reductase

Enzyme that reduces conjugated double bonds in polyunsaturated fatty acids using NADPH

Odd-chain fatty acids

Fatty acids that yield propionyl-CoA in final step of beta-oxidation

Propionyl-CoA

Three-carbon product converted into succinyl-CoA for entry into TCA cycle

Propionyl-CoA carboxylase

Enzyme converting propionyl-CoA to methylmalonyl-CoA (requires biotin)

Methylmalonyl-CoA mutase

Enzyme converting methylmalonyl-CoA to succinyl-CoA (requires vitamin B12)

Succinyl-CoA

TCA cycle intermediate derived from odd-chain fatty acids and usable in gluconeogenesis

Glucogenic fatty acids

Odd-chain fatty acids that can contribute to glucose production via succinyl-CoA

Peroxisomal beta-oxidation

Fatty acid oxidation pathway in peroxisomes for very long-chain fatty acids

Acyl-CoA oxidase

Enzyme in peroxisomes that transfers electrons to oxygen forming hydrogen peroxide

Catalase

Enzyme that breaks down hydrogen peroxide into water and oxygen in peroxisomes

Very long-chain fatty acids (VLCFA)

Fatty acids too long for mitochondrial oxidation, first shortened in peroxisomes

Octanoyl-CoA

Intermediate product transferred from peroxisomes to mitochondria for further oxidation

Hydrogen peroxide (H₂O₂)

Reactive byproduct of peroxisomal oxidation

Energy from fatty acids

Produced through NADH, FADH₂, and acetyl-CoA entering oxidative phosphorylation and TCA cycle