Template:Leucine metabolism in humans

Leucine metabolism in humans

File:HMB biosynthesis and metabolism diagram - no labels.svg

[[Leucine|L-Leucine]]

Branched-chain amino
acid aminotransferase

α-Ketoglutarate

Glutamate

Glutamate

Alanine

Pyruvate

Muscle: α-Ketoisocaproate (α-KIC)

Liver: α-Ketoisocaproate (α-KIC)

Branched-chain α-ketoacid
dehydrogenase (mitochondria)

KIC-dioxygenase
(cytosol)

Isovaleryl-CoA

β-Hydroxy
β-methylbutyrate
(HMB)

Excreted
in urine
(10–40%)

HMB-CoA

β-Hydroxy β-methylglutaryl-CoA
(HMG-CoA)

β-Methylcrotonyl-CoA
(MC-CoA)

β-Methylglutaconyl-CoA
(MG-CoA)

CO₂

CO₂

O₂

CO₂

H₂O

CO₂

H₂O

(liver)
HMG-CoA
lyase

Enoyl-CoA hydratase

Isovaleryl-CoA
dehydrogenase

MC-CoA
carboxylase

MG-CoA
hydratase

HMG-CoA
reductase

HMG-CoA 
synthase

β-Hydroxybutyrate
dehydrogenase

Mevalonate
pathway

Thiolase

Unknown
enzyme

β-Hydroxybutyrate

Acetoacetyl-CoA

Acetyl-CoA

Acetoacetate

Mevalonate

Cholesterol

The image above contains clickable links

Human metabolic pathway for HMB and isovaleryl-CoA relative to [[leucine|L-leucine]]. Of the two major pathways, L-leucine is mostly metabolized into isovaleryl-CoA, while only about 5% is metabolized into HMB.

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